The Nervous System
Chapter 11
Parts of the Nervous System
CNS: brain & spinal cord
– Receives & processes information,
– initiates effector responses
PNS: nerves outside CNS
Central N.S.
Brain
Spinal cord
– Sensory (body- receptors CNS)
– Motor (CNS  body- effector cell)
Sensory
Motor
– Somatic division: controls
skeletal muscle
– Autonomic division: controls
Somatic
Autonomic
cardiac muscles, smooth
- parasympathetic
- sympathetic
muscles and glands
– Parasympathetic (calming)
– Sympathetic (fight-orPeripheral N.S.
flight)
From Cells to Organ Systems
Purpose: transmit, control, maintain, process
• neuron: nerve cell
– Sensory: sends info to CNS
– Motor: carries CNS directions to the body
– Interneuron: relays messages between sensory
and motor neurons
• glial cell: of fifferent types; supports/protects
neurons
– Some form myelin sheaths- e.g. Schwann cells
(PNS); oligodendrocytes (CNS)
– speeds up transmission, & helps damaged/severed
axons regenerate
Q: How does structure go with function?
Myelinated neuron
Figure 11.7a
From stimulus to response
Figure 11.2
Skin
Receptor
Dendrite
Axon
Muscle
Axon bulb
Axon terminals
Axon
Sensory
neuron
Impulse direction
Motor
neuron
Axon hillock
Dendrites
Interneuron
Cell
body
Dendrites
Axon
Cell body
Brain and spinal cord
Cell body
• Stimulus triggers sensory receptor
on dendrite of sensory neuron
• The impulse is sent towards the
cell body
• Axons transmit the signal away
from the cell body eventually to
interneuron
• Interneuron “processes” info then
sends impulse to a motor neuron
• Motor neuron transmits to an
effector (muscle or gland)
• Muscle or gland responds
Synapse
• Is a junction, between neurons or
neuron and effector cell
• Between neurons it consists of:
• 1.Axon terminal of presynaptic
(transmitting) neuron
2.postsynaptic (receiving) neuron
• 3.The two neurons are separated by
a space (synaptic cleft)
• The nerve impulse triggers the
release of neurotransmitters from
vesicles in axon teminal
• Neurotransmitters will lead to
initiation of an action potential (
nerve signal in second neuron)
Figure 11.8
Central Nervous System; brain and
spinal cord
Figure 11.13
Cerebral cortex
• Outer layer of cerebrum
• outer region is grey matter
(processing, etc.): contains
functional areas
White matter
• Inner region is white matter
(receiving/sending signals)
Parietal lobe
• Interprets sensory
information from skin
Occipital lobe
• Processes visual
information
Temporal lobe
• Interprets auditory
Frontal lobe
information
• Initiates motor activity
• Responsible for speech • Comprehends language
• Conscious thought
Figure 11.16b
Central Nervous System
Central Nervous system: brain and spinal cord
• CNS protection
– Bone: skull and vertebrae
– Meninges: dura mater, arachnoid, and pia mater
– Cerebrospinal fluid: protective cushion- produced by
capillaries
– Blood–brain barrier: allows limited material across
membrane of capillary cells
The brain processes and acts on information
Figure 11.15
FOREBRAIN
Cerebrum
• Coordinates language
• Controls decision
making
• Produces emotions and
conscious thought
MIDBRAIN
• Relays visual
and auditory
inputs
Corpus callosum
• Bridges the
two cerebral
hemispheres
Thalamus
• Receives, processes
and transfers motor
information/sensations
Limbic System;
Involved in
emotions
HINDBRAIN
Pons
• Connects cerebellum, spinal cord
with higher brain centers
•
Medulla oblongata
• Has vital centers for
breathing, heart rate
Cerebellum
• Controls basic
and skilled
movements
Coordinates movement
Q: Which part of the brain classifies humans as “intelligent” beings?
Peripheral Nervous System
Peripheral Nervous system
• Transmits information between tissues and CNS
– Mediated via nerves (collection of neurons)
– Nerve function depends on its origin and destination
• Two types of peripheral nerves
– 12 cranial nerves: connects directly to the brain
– 31 spinal nerves: connects to the spinal cord
• Sensory neurons enter spinal cord
• Motor neurons exits spinal cord
Peripheral Nervous System
PNS Somatic division controls skeletal muscles
controls voluntary movements
Includes spinal reflexes
– Involuntary responses
– Does not require conscious
thought
Central N.S.
Brain
Spinal cord
Sensory
Motor
Autonomic
Somatic
- parasympathetic
- sympathetic
-skeletal muscle
-spinal reflexes
Peripheral N.S.
Peripheral Nervous System
PNS Autonomic division:
Sympathetic and parasympathetic motor divisions
– Oppose each other
Central N.S.
Brain
– Helps maintain homeostasis
– Control functions in cardiac
Spinal cord
muscles, glands, smooth muscles,
etc.
Motor
– Sympathetic stimulates/arouse Sensory
– Parasympathetic relaxes
Autonomic
Somatic
- parasympathetic
- sympathetic
-skeletal muscle
-spinal reflexes
Peripheral N.S.
Sympathetic and parasympathetic motor divisions