•Nervous system – made of cells that have an ability to depolarize
•Central nervous system – brain & spinal cord
•Peripheral nervous system – outside of the CNS with sensory & motor components
•Autonomic division has sympathetic & parasympathetic divisions
•Both neurons & glia cells are in the nervous system
•All neurons have a cell body, dendrites, and one axon
•Neurons are classified as sensory, interneurons or motor neurons depending on
function
•A resting neuron has potential of - 70 millivolts, it is more negative in the
cytoplasm than the outside of the cell
•Sodium ions line up on the outside of the membrane & potassium ions on inside makes a membrane potential
•Axon originates from the axon hillock & ends as an axon bulb
•The potential of the neuron is maintained by sodium-potassium pumps that pump
sodium out & potassium in to get to the resting potential of -70 millivolts
•A change in potential happens when ions flow through the membrane – opening
and closing of ion channels that let ions pass through the cell membrane change the
potential
•summation of the charges of ion movement occurs, and if potential rises +15 from 70 to -55 (the threshold), that causes an ‘action potential’
•The action potential spreads through the neuron, opening sodium ion channels so
they move inside, spreading the -55mV, potassium ions move out
Then the membrane has to recharge - the ‘absolute refractory period
•Action potentials are all-or-none
•Neurons release their neurotransmitter at the end of the axon because of calcium
ions, the -55mV causes calcium ions to exit storage sites, which makes the
neurotransmitter move to the synapse and get released
•The neurotransmitter effects the postsynaptic neuron – it binds to the postsynaptic
membrane & either opens ion channels or begin enzymatic pathways
•Postsynaptic neurons integrate & process information
•31 pair of spinal nerves and 12 pair of cranial nerves connect the body to the
central nervous system
•Glial cells support neurons: astrocytes hold neurons & blood vessels in place, like a
living scaffold
•An insulating myelin sheath is made by the cell membranes of schwann cells or
oligodendrocytes
•Myelin speeds transmission by saltatory conduction
•In multiple sclerosis myelin is damaged, usually due to autoimmune process
•In amyotrophic lateral sclerosis – Lou Gherig’s disease, motor neurons are affected
•Humans have 12 pairs of cranial nerves and 31 pairs of spinal nerves
•Most nerves have both motor & sensory components
•CNS is covered by meninges – dura mater, arachnoid, pia mater
•Cerebrospinal fluid is located in the subarachnoid space
•The blood brain barrier prevents everything except alcohol, caffeine, nicotine,
cocaine, anesthetics to cross into the CNS
Cerebrospinal fluid is between the arachnoid & pia
•Spinal cord relays information to & from the brain
•The CNS developed as a tube, approximately day 15
•The brain developed from cranial enlargements of the tube
•Parts are:
•Spinal cord
•Medulla
•Cerebellum
•Pons
•Midbrain
•Diencephalon
•Cerebral hemispheres
•Spinal cord has nerve tracts – sensory going up to the brain, motor coming down
from the brain
•Gray matter is made of neurons white matter made of axons & dendrites, spinal
nerves exit between the vertebrae
•Medulla oblongata – controls automatic functions
•Cardiovascular & respiratory centers
•Vagus nerve - Pyramidal decussation
•Cerebellum – controls movements
•Pons – tracts to cerebellum and spinal cord
•Midbrain has sites involved with vision & hearing
•Reticular formation coordinates movements, helps modulate pain, & activates the
brain
•Sleep – reticular activating system - Serotonin induces sleep by inhibiting neurons
that arouse the brain - Epinephrine inhibits serotonin
•Stage 1 – pupils constrict, breathing slows, heart rate slows
•Stage 2 – skeletal muscles relax, eye & body movements cease
•Stage 3 – sleep deepens, heart & respiratory rate slow more
•Stage 4 – lowest rates, body temperature falls
•REM – dreaming - increase of heart & respiratory rates, and increase of blood flow
to the brain but the boy muscles go limp and eyes move rapidly
•REM every 90 minutes for 20 minutes at a time
•Thalamus is a relay station up to the cerebral cortex & hypothalamus controls
autonomic function
•Cerebral cortex – frontal, temporal, parietal, occipital lobes
•Primary motor & sensory cortex, visual cortex, executive function, storage of
memories
•Limbic system is a circular pathway that controls and affects emotions & memory,
learning & emotional behavior
•Psychoactive drugs – can cross blood brain barrier
•Influence concentrations of actions of brain neurotransmitters
•Inhibit or mimic actions
•Cocaine blocks dopamine reuptake
•Dependence – crave feelings and alter behavior to obtain
•Tolerance – need to use more – liver develops more detoxifying enzymes
•Addiction – need to continue use
•Withdrawal – symptoms that occur if drug is removed
•Concussion – brief period of unconsciousness
•Spinal cord injury
•Encephalitis, meningitis, rabies
•Epilepsy – recurring abnormal activity
•Parkinson’s – loss of dopamine
•Alzheimer’s – loss of acetylcholine
•Huntington’s – loss of inhibitory neuron transmitter
•Stimulus – sensory input that affects a receptor that converts it - brought by
dendrites to nerve cell body
•Sensation – awareness of stimulus
•Perception – understanding the sensation
•Dendrites of sensory neurons bring in information to the CNS
•Each neuron has its own special modality
•Spinal reflexes use muscle spindles
•Muscle spindles are sensory endings that monitor the amount of stretch of a
muscle
•Golgi tendon organs
•There are many types of sensory receptors: mechanoreceptors, thermoreceptors,
pain receptors, chemoreceptors, photoreceptors
•Receptors can adapt - Somatic sensations in skin
•Pain receptors – the brain can interpret pain from organs as referred pain to
another body part
•Taste comes from chemoreceptors: salty, sweet, sour, bitter, umami
•Smell – chemoreceptors bind with odorants
•Olfactory receptor cells have dendrites
•Chemicals enter nasal cavity and dissolve in the mucus
•Hearing & balance come from mechano-receptors with hairs
•Intensity – amplitude, pitch – frequency of sound waves
•Ear changes sound waves to fluid waves
•Vestibular system relies on position or movement direction to depolarize
•Vision begins with the rod & cone photoreceptors
•Visual signal divides at the optic chiasm into visual fields
•Peripheral nervous system has somatic & autonomic divisions
•Autonomic division is divided into sympathetic & parasympathetic parts
•Autonomic nervous system is composed of sympathetic & parasympathetic
divisions
•Preganglionics release acetylcholine onto nicotinic receptors
•Postganglionics – acetylcholine or epinephrine/ norepinephrine
•Fight or flight
•Rest & digest
•Autonomic system controls visceral function
•Preganglionic neurons go from the CNS to ganglia (collections of neurons) in the
PNS where the post-ganglionic neurons innervate smooth muscles or glands
•Sympathetic NS is fight or flight – thoracolumbar region
•Parasympathetic NS is rest & digest – cranial & sacral regions
•Work antagonistically to maintain homeostasis
Endocrine glands
•Endocrine glands make hormones
•Hormones are classified as either steroid or nonsteroid
•Steroid hormones can go through cell membranes
•Nonsteroid rely on second messenger receptors to activate the target cell
•Negative feedback is a control mechanism
•Hypothalamus controls the pituitary gland
•Pituitary controls many endocrine glands
•Posterior pituitary makes ADH & oxytocin
•Anterior pituitary controls adrenal cortex, thyroid, reproductive organs, formation
of milk & growth
•Liver’s hepatic portal system is important for glucose control
•The pancreas makes glucagon and insulin in response to blood glucose levels, and
somatostatin
If blood glucose levels fall, the hypothalamus stimulates the pituitary to release
ACTH which stimulates the adrenal cortex to release glucocorticoids, (steriods) that
will make the blood glucose levels increase
•Adrenal cortex secretes mineralo-corticoids, glucocortioids, and androgens
•Adrenal medulla secretes epinephrine & norepinehrine, augments fight or flight
response
•Thyroid gland secretes thyroxine & triiodothyronine that increase the basal
metabolic rate – how fast calories are burned
•Calcitonin & parathyroid hormone & vitamin D affect bone health
•Thymus gland trains T lymphocytes
•Pineal gland
•Atrial natriuretic peptide
•Gastrin, secretin, cholecystokinin
•Erythropoietin, renin
•Mitosis is the formation of cells during growth and development, and to replenish
the cells of the body
•A mother cell will form into 2 identical daughter cells
•Diploid cells form diploid cells
•Hyperplasia refers to increased cell mitosis
•Metaplasia is what happens when the cell type changes into a different cell type –
precancerous
•Dysplasia is when the cell structure becomes abnormal
•With cancer, the cells grow and divide uncontrollably
•Proto-oncogenes promote normal mitosis and cell growth, can become oncogenes
that cause cancerous growth
•Tumor suppressor genes usually inhibit abnormal growth, but they can mutate and
become useless
•Carcinogens affect these controller genes - viruses, chemicals, radiation are
examples
Meiosis
Seminiferous Tubules
•Male reproductive organs include the testes, epididymis, vas deferens, ejaculatory
duct, seminal vesicle, urethra, prostate, penis
•Seminal vesicles produce fructose & prostalandins
•Prostate gland makes an alkaline secretion
•100-300 million sperm/ejaculate
•Hypothalamus GnRF – FSH, LH
•Female reproductive system organs include:
•Ovaries
•Fallopian tubes
•uterus
•vagina
•1 million oocytes are in the ovary at birth
•All are primary oocytes
•300,000 remain by puberty
•Oocytes develop in follicles
•FSH stimulates follicle growth & production of estrogen
•Estrogen stimulates growth of the endo-metrium – lining of the uterus – to prepare
for possible implantation
•Estrogen causes a surge in LH, then ovulation, with the 1st meiotic division
•Remaining follicle cells form a corpus luteum that secretes both progesterone &
estrogen
•Progesterone makes the endometrium secretory but also inhibits FSH & LH
•Drops in estrogen & progesterone cause menstruation
•If fertilized, human chorionic gonadotropin stimulates the corpus luteum to secrete
more estrogen & progesterone
•Birth control pills have synthetic progesterone & estrogen that inhibit FSH & LH
release so that ovuation doesn’t take place
•STD’s•Bacterial – gonorrhea, syphilis, chlamydia
•Viral - HIV, hepatitis B, Genital herpes, HPV
•Yeast – candida
•Protozan - trichomonas