BIOL 2020
HUMAN
ANATOMY &
PHYSIOLOGY II
Dr. Tyler Evans
Email: tyler.evans@csueastbay.edu
Office: S Sci 350
Office Hours: F 8:30-11:30 or by appointment
Website: http://evanslabcsueb.weebly.com/
Phone: 510-885-3475
LAST LECTURE
THE SPECIAL SENSES
• the PERIPHERAL NERVOUS SYSTEM (PNS) provides links from and to the world
outside our bodies
• the PNS includes all neural structures outside the brain and spinal cord including
sensory receptors, peripheral nerves and motor endings
• input into the PNS comes from SENSORY RECEPTORS that are specialized to
respond to changes in their environment
• receptors can be classified in three different ways:
1.
STIMULUS THEY DETECT
MECHANORECPTORS: respond to mechanical force such as touch and pressure
THERMORECEPTORS: respond to temperature changes
PHOTORECEPTORS: respond to light and found in the retina of the eye
CHEMORECEPTORS: respond to chemicals in solution and involved in smell and taste
NOCICEPTORS: responds to damaging stimuli that result in pain
LAST LECTURE
SENSORY RECEPTORS
• regardless of detected, stimulus, location or structure of the receptor, each
sensory receptor takes incoming stimuli and converts them into changes in
membrane potential
• typically, specialized receptor proteins in the cell membrane absorb energy of
the incoming stimulus and undergo a conformation change
• this conformational change triggers a signal transduction pathway that opens or
closes ion channels in the membrane and creates an ACTION POTENTIAL
LAST LECTURE
DETERMINING STIMULUS INTENSITY
• because action potentials will not change their signal intensity (recall this is an
all-or-nothing response), stimulus intensity is determined by the number of
activated receptors on the membrane of a sensory cell
• the weakest stimulus that will produce an action potential is called the
THRESHOLD OF DETECTION
• e.g. some photoreceptors can detect a single photon of light
• In contrast, at RECEPTOR SATURATION all of the receptors on a sensory cell are
activated and an increase in stimulus intensity will have no effect
Difference between
threshold of detection and
receptor saturation is called
the DYNAMIC RANGE, which
is depicted in this graph
LAST LECTURE
PHOTORECEPTORS
PHOTORECEPTORS: are sensory cells that detects incoming light. A quarter billion
are found in the retina and come in two forms:
RODS: used for dim-light and peripheral vision because they are more numerous
and more sensitive tot light.
• however, rods do not provide sharp vision or color vision
CONES: are photoreceptors for bright light and provide high resolution color vision
Fig 15.6 pg 550
LAST LECTURE
PHOTOTRANSDUCTION
• photopigments are a combination of a light absorbing molecule called RETINAL
(a derivative of VITAMIN A) and an OPSIN protein
• for example, RHODOPSIN is the photopigment found in rods
• when retinal is struck by light it undergoes a conformational (shape) change:
• photoexcitation
causes 11-CISRETINAL to change
to 11-TRANSRETINAL
• same process
occurs in cones,
but using different
photopigments
Fig 15.16 pg 560
TODAY’S LECTUER: THE SPECIAL SENSES
THE EAR: HEARING AND BALANCE
• structures controlling hearing and balance are located in the ear, but
receptors for each sense respond to different stimuli and operate
independently
• the ear is divided into three major areas:
1. EXTERNAL EAR
• the external ear is composed of the
PINNA and EXTERNAL ACOUSTIC
MEATUS
• the pinna is the fleshy outside of the
ear and is composed of elastic
cartilage tissue and funnels sound into
the ear
• the external acoustic meatus is a short
curved tube extending from the pinna
to the ear drum
• secretes wax that protects inner
ear
Fig 15.24 pg 571
THE SPECIAL SENSES
THE EAR: HEARING AND BALANCE
• sound waves entering the external meatus contact the TYMPANIC
MEMBRANE (i.e. ear drum)
• tympanic membrane is thin connective tissue shaped like a flattened cone
• sound waves cause the tympanic membrane to vibrate ,which serves to
transfer the sound energy to the bones of the middle ear
Fig 15.24 pg 571
THE SPECIAL SENSES
THE EAR: HEARING AND BALANCE
2. MIDDLE EAR: is a small air-filled cavity that houses the three smallest bones in
the human body: the MALLEUS, INCUS and STAPES (collectively called the
AUDITORY OSSICLES)
• these three bones transfer vibrations from sound waves to the inner ear through
an opening called the OVAL WINDOW
THE SPECIAL SENSES
THE EAR: HEARING AND BALANCE
3. INNER EAR: called the labyrinth because of its complicated structure
• the oval window opens to a VESTIBULE, the central cavity
• suspended in the vestibule are two sacs: the SACCULE and UTRICLE
• also extending from the vestibule are three SEMICIRCULAR CANALS
• the saccule, utricle and semicircular canals are involved in equilibrium
• also extending from the vestibule is the coiling COCHLEA
• running through the cochlea is the COCHLEAR MEMBRANE that houses the
organ of hearing the SPIRAL ORGAN
Fig 15.26 pg 573
THE SPECIAL SENSES
PHYSIOLOGY OF HEARING
• sounds causes vibration in air that enter the ear and vibrates the
tympanic membrane
• vibrations are transferred to the tiny bones of the ear
• vibrations in bones push fluid of inner ear against
membranes
• tiny hairs on the membranes pivot and this triggers the
release of a nerve impulse
• nerve impulse travels to the brain where it is interpreted
THE SPECIAL SENSES
PHYSIOLOGY OF HEARING
vibrations displace
the membrane of
cochlea
Fig 15.30 pg 577
THE SPECIAL SENSES
TRANSMISSION OF SOUND
• as the STAPES rocks back and forth,
it sets the fluid within the
COCHLEA, called PERILYMPH, in
motion
• this induces a pressure wave which
travels through the perilymph
• low frequency sounds travel the
entire length of the cochlea and
stimulate parts of the BASILAR
MEMBRANE furthest away from the
oval window
• high frequency sounds stimulate
the basilar membrane much closer
to the window
Fig 15.30 pg 577
THE SPECIAL SENSES
RECEPTOR EXCITATION
• basilar membrane is covered with hearing receptors called HAIR CELLS, which
are directly linked to a neuron
• hair cells have one long KINOCILIUM and
several shorter STEREOCILIA and are
arranged in a tight bundle connected by
fibers called TIP LINKS
• as sound waves move through the
perilymph, it causes the stereocilia and
kinocilium to pivot (they are rigid so don’t
bend)
Fig 15.31 pg 578
THE SPECIAL SENSES
RECEPTOR EXCITATION
• bending of the sterocilia puts pressure on the tip links which in turn open ion
channels causing a change in membrane potential and the release of the
neurotransmitter GLUTAMATE
• when the hair cells return to resting position the ion channels close and the
membrane repolarizes
THE SPECIAL SENSES
EQUILIBRIUM AND ORIENTATION
• equilibrium sensors are in the semi-circular canals, utricle, and saccule and
collectively referred to as the VESTIBULAR APPARATUS
• receptors in the semi-circular canals monitor changes in the rotation of the
head called our SENSE OF DYNAMIC EQUILIBRIUM
• receptors in the utricle and saccule monitor linear acceleration and position of
head with respect to gravity called our SENSE OF STATIC EQUILIBRIUM
(because gravity is constant)
• the utricle and saccule each contain a MACULA embedded in their walls, which
acts as receptors to monitor linear acceleration and position of head with
respect to gravity
THE SPECIAL SENSES
EQUILIBRIUM AND ORIENTATION
• each macula is a flattened epithelial
patch covered with hair cells
• the hair cells are embedded in an
overlying OTOLITH MEMBRANE, a jelly
like substance studded with tiny stones
called OTOLITHS
• head movement influences the otolith
membrane, in turn causing the
stereocilia to pivot and change
membrane potential
• in the utricle the hairs are
horizontal and respond to
acceleration (e.g. starting to run)
• in the saccule the hairs are vertical
and respond to gravity changes
(e.g. an elevator)
Fig 15.33 pg 580
THE SPECIAL SENSES
EQUILIBRIUM AND ORIENTATION
• the direction the hair pivot causes different signals to be generated:
• if movement is toward the kinocilium non-selective ion channels on the
stereocilia OPEN
• this depolarization increases the frequency of action potential
• if movement is away from kinocilium, non-selective ion channels on the
stereocilia CLOSE
• this hyperpolarization decreases the frequency of action potentials
TOWARD = OPEN = DEPOLARIZATION
AWAY = CLOSE = HYERPOLARIZATION
THE SPECIAL SENSES
EQUILIBRIUM AND ORIENTATION
• the receptor for rotational movement of the head is called the CRISTA
AMPULLARIS
• these are found in the semi-circular canals and because of the canals shape the
hair cells can be oriented in all three planes and monitor a greater range of
motion
• the crista ampullaris differs slightly in structure in that the hair cells are housed in
a gelled mass called an AMPULARY CUPULA
Fig 15.35 pg 582
THE SPECIAL SENSES
EQUILIBRIUM AND ORIENTATION
• despite this difference in structure, the activation of the crista ampullaris follows
the same principles as described for the macula
Fig 15.35 pg 582
THE SPECIAL SENSES
PATHOLOGIES OF HEARING & EQUILIBRIUM
• MOTION SICKNESS: conflicting information between sensory inputs
• e.g. inside a boat during a storm your eyes will indicate your body is fixed,
but vestibular apparatus is detecting movement
• CONDUCTION DEAFNESS: something prevents transmission of sound waves
through the fluid of inner ear (e.g. wax or perforated tympanic membrane)
• SENSORINEURAL DEAFNESS: any damage to the neuronal parts of the ear (e.g.
hair cells)
• TINNITUS: ringing in the ears in the absence of sound. A sign of nerve
degeneration of inflammation of the middle or inner ear
• MENIERES SYNDROME: attacks of vertigo, nausea and vomitting and balance is
severely disturbed.
• may result from excess fluid in the ear and can be treated by draining
POTENTIAL BREAK
PERIPHERAL AND AUTONOMIC NERVOUS SYSTEM
CHAPTER 13 & 15
• we have described how the special senses are connected to neurons and the
CNS (i.e. INPUT)
• but other nerve fibers of the PNS connect to muscles in the MOTOR DIVISION
of the PNS (i.e. OUTPUT)
Fig 11.2 pg 388
PERIPHERAL AND AUTONOMIC NERVOUS SYSTEM
CHAPTER 13 & 15
• but other nerve fibers of the PNS connect to muscles in the MOTOR DIVISION of
the PNS (i.e. OUTPUT)
• those that innervate voluntary muscles (i.e. under conscious control) form
NEUROMUSCULAR JUNCTIONS and are part of the SOMATIC NERVOUS
SYSTEM
• here axons branch and attach to a single muscle fiber
NERVES, REFLEXES and the AUTONOMIC NERVOUS SYSTEM
REFLEXES
• some of the actions of the somatic nervous system are REFLEXES, which can
be either:
1. INBORN: rapid predictable response to a stimulus that is built into our
neural anatomy (e.g. pulling away after being splashed with boiling water)
• prevent having to think of all the little details that keep us alive
2. LEARNED (ACQUIRED): results from repetition or practice (e.g. complex
sequence of reactions when experienced driver drives a car)
*in reality the differences between these two reflexes are cloudy
NERVES, REFLEXES and the AUTONOMIC NERVOUS SYSTEM
REFLEX ARCS
• reflexes occur over highly specific neural pathways called REFLEX ARCS, consisting
of five essential components:
1. RECEPTOR: site of stimulus action
2. SENSORY NEURON: transmits impulses to the CNS
3. INTEGRATION CENTER: may be a simple synapse between a sensory and motor
neuron (MONOSYNAPTIC REFLEX) or become more complex with strings of
interneurons in between (POLYSYNAPTIC REFLEX)
4. MOTOR NEURON: transmit signals from the integration center to the muscle or
other organ
5. EFFECTOR: muscle or gland that responds to the signal
Fig 13.15 pg 513
NERVES, REFLEXES and the AUTONOMIC NERVOUS SYSTEM
REFLEXES
• the STRETCH REFLEX: by sending signals to muscles, the brain sets the muscle
length (when muscles contract they shorten and are longer when relaxed)
• the stretch reflex makes sure the muscle stays at appropriate length
• e.g. KNEE-JERK REFLEX: helps prevent your knees from buckling when you stand
upright. When you begin to stand and your knees buckle causing the quadriceps
muscle lengthen, the reflex signals the quadriceps to contract to support our
weight without having to think about it.
• this reflex can be triggered by a sudden jolt to the tendon:
Fig 13.18 pg 516
NERVES, REFLEXES and the AUTONOMIC NERVOUS SYSTEM
REFLEXES
• FLEXOR or WITHDRAWL REFLEXES: initiated by a painful stimulus causing
automatic withdrawal of the effected body part (e.g. prick of the finger)
• can be over-ridden by the brain if you are expecting a painful stimulus, (e.g. the
prick of a needle when giving blood)
e.g. a stranger unexpectedly grabs your arm
Fig 13.20 pg 518
NERVES, REFLEXES and the AUTONOMIC NERVOUS SYSTEM
REFLEXES
WHY WOULD A DOCTOR CHECK
RELFEXES?
NERVES, REFLEXES and the AUTONOMIC NERVOUS SYSTEM
THE AUTONOMIC NERVOUS SYSTEM
CHAPTER 14
• stability of our internal environment depends largely on the AUTONOMIC
NERVOUS SYSTEM, the system of motor neurons controlling smooth muscle,
cardiac muscle and glands
• signals stream from various organs and autonomic nerves make the necessary
adjustment to ensure optimal body function
• most of the fine tuning occurs without our awareness
• e.g. dilating of pupils in the eye
• e.g. shunting of blood to organs in need
NERVES, REFLEXES and the AUTONOMIC NERVOUS SYSTEM
THE AUTONOMIC NERVOUS SYSTEM
The ANS has two divisions:
1. PARASYMPATHETIC: keeps energy use as small as possible and directs housekeeping functions
• digesting food
• eliminating feces and urine
2. SYMPATHETIC: often called fight-or-flight response, this division is active
when we are excited or find ourselves in dangerous situations
• several reactions occur when the sympathetic nervous system is stimulated
• increase in heart rate
• cold sweaty skin
• dilated pupils
• temporarily dampens non-essential activities (e.g. digestion)
• liver releases more glucose into the blood
• dilates branchioles to increase ventilation
NERVES, REFLEXES and the AUTONOMIC NERVOUS SYSTEM
ANS PHYSIOLOGY
• many signals in the ANS are transmitted by two neurotransmitters:
1. ACETYLCHOLINE (ACh): fibers that release acetylcholine are called
CHOLINERGIC FIBERS
2. NOREPINEPHRINE: fibers that release acetylcholine are called ADRENERGIC
FIBERS
• neither of these hormones are consistently stimulatory or inhibitory, because
they bind to different types of receptors that trigger different effects
ACETYLCHOLINE
NOREPINEPHRINE
NERVES, REFLEXES and the AUTONOMIC NERVOUS SYSTEM
ANS RECEPTORS
• there are two types of CHOLINERGIC RECEPTORS that bind acetylcholine (named
for drugs that mimic the effects of acetylcholine):
1.
2.
NICOTINIC: when Ach binds to these receptors the effect is always stimulatory
MUSCARINIC: when Ach binds to these receptors the effect can be either
stimulatory or inhibitory (depending on target organs and receptor subclass)
• there are also two major types of ADRENERGIC RECEPTORS that bind
norepinephrine:
1.
2.
ALPHA ADRENERGIC
BETA ADRENERGIC
• there are several sub-types for each receptor class
• again, binding can elicit stimulatory or inhibitory effects
NERVES, REFLEXES and the AUTONOMIC NERVOUS SYSTEM
ANS RECEPTORS
• many medical drugs are the targets of cholinergic and adrenergic receptors:
e.g. ATROPINE: blocks muscarinic receptors and is commonly administered before
surgery to prevent salivation and respiratory secretions.
• optometrists also use atropine to dilate pupils for eye exams
NERVES, REFLEXES and the AUTONOMIC NERVOUS SYSTEM
UNIQUE ROLES OF SYMPATHETIC DIVISION
• the adrenal gland, sweat glands and arrector pili muscles of the skin, kidneys
and most blood vessels are only innervated by sympathetic fibers
• think sweating under stress and goose-bumps during fear
• other uniquely sympathetic responses include:
1. THERMOREGULATORY RESPONSES TO HEAT
• heat causes vessels near skin to dilate and activates sweat glands, both of which
work to cool the body.
2. RELEASE OF RENIN FROM KIDNEYS
• RENIN is an enzyme that acts as a signal for the body to increase blood pressure
3. METABOLIC EFFECTS
• increases metabolic rate
• raises blood glucose levels
• mobilizes fat stores for energy use
NERVES, REFLEXES and the AUTONOMIC NERVOUS SYSTEM
INTERACTIONS OF DIVISIONS OF THE ANS
• most target organs can receive inputs from both divisions:
ANTAGONISITC (i.e. opposite) RESPONSES: are most clearly seen via activities on
the heart, respiratory systems and gastrointestinal tract.
e.g. in a fight or flight response, the sympathetic division increases heart
rate and dilates airways but decreases digestion and excretion
COOPERATIVE RESPONSES: best example occurs in the external genitalia
e.g. parasympathetic stimulation dilates blood vessels in the external
genitalia while sympathetic stimulation causes male ejaculation or reflex
contractions of the vagina
NERVES, REFLEXES and the AUTONOMIC NERVOUS SYSTEM
INTERACTIONS OF DIVISIONS OF THE ANS
NERVES, REFLEXES and the AUTONOMIC NERVOUS SYSTEM
PATHOLOGIES OF THE ANS
HYPERTENSION (high blood pressure): may result from an overactive sympathetic
vasoconstriction response promoted by continuous exposure to stress
Causes heart to work harder and can contribute to heart disease
RAYNAUD’S DISEASE: intermittent attacks where
the fingers/toes become pale and then cyanotic
and painful
• commonly caused by stress or exposure to cold
• can be extreme such the tissue become devoid
of blood and can die
AUTONOMIC DYSREFLEXIA: life threatening condition and is characterized by an
uncontrolled increase in blood pressure that may rupture a blood vessel in the
brain
NERVES, REFLEXES and the AUTONOMIC NERVOUS SYSTEM
GLOSSARY: OVERVIEW OF CRANIAL NERVES
I.
II.
III.
IV.
V.
VI.
VII.
VIII.
IX.
X.
XI.
XII.
OLFACTORY: sensory nerves of smell
OPTIC: sensory nerve of vision
OCCULOMOTOR: controls the six muscle that move the eye
TROCHLEAR: innervates one of the eye muscles
TRIGEMINAL: has three branches and supplies sensory nerves to the face and
chewing muscles
ABDUCENS: controls eye muscle that turn the eye laterally
FACIAL: control muscles involved in facial expression
VESTIBULOCOCHLEAR: sensory nerve for hearing and balance
GLOSSOPHARYNGEAL: name means “tongue” and “pharynx” (occurs at back of
throat)
VAGUS: only nerve to extend beyond the head and innervate parts of the heart,
lung and viscera including the, kidneys and intestine
ACCESSORY: considered an extension of the vagus nerve and thus has similar
target organs
HYPOGLOSSAL: runs “under the tongue” and innervates muscles of the tongue
Note: Table 13.2 pg 494-500 explain the structure and function of cranial nerves in more detail
FOR REVIEW TONIGHT
• Understand the structure and function of components
of the ear
• Understand signal transduction through hair cells
• Understand the cells and tissues involved in
equilibrium
• Understand the steps and purpose of a reflex arc
• Understand the functions of the two divisions of the
autonomic nervous system
NEXT LECTURE
BLOOD I