The Nervous System

Chapter 11

Parts of the Nervous SystemCNS: brain & spinal cord– Receives & processes information,– initiates effector responses

PNS: nerves outside CNS– Sensory (body- receptors CNS)– Motor (CNS body- effector cell)

– Somatic division: controls skeletal muscle

– Autonomic division: controls cardiac muscles, smooth muscles and glands

– Parasympathetic (calming)– Sympathetic (fight-or-

flight)

Central N.S.Brain

Spinal cord

Peripheral N.S.

MotorSensory

Autonomic- parasympathetic- sympathetic

Somatic

From Cells to Organ Systems

Q: How does structure go with function?

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 -

Figure 11.7a

Myelinated neuron

Sensoryneuron

Dendrite

Receptor

Cell body

Axon

Axon terminalsAxon bulb

Dendrites

Dendrites

Cellbody

Cell body

Axon

Axon

Axon hillock

Interneuron

Brain and spinal cord

Motorneuron

Skin

Muscle

Impulse direction

From stimulus to responseFigure 11.2 • 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

Figure 11.8

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 11.13

Central Nervous System; brain and spinal cord

Parietal lobe• Interprets sensory information from skin

Occipital lobe• Processes visual information

Frontal lobe• Initiates motor activity• Responsible for speech• Conscious thought

Temporal lobe• Interprets auditory information• Comprehends

language

Figure 11.16b

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)

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

Central Nervous System

Figure 11.15

FOREBRAIN

Thalamus • Receives, processes

and transfers motorinformation/sensations

Corpus callosum • Bridges the

two cerebralhemispheres

Cerebrum • Coordinates language • Controls decision

making • Produces emotions and

conscious thought

MIDBRAIN • Relays visual

and auditoryinputs

HINDBRAIN

Cerebellum • Controls basic

and skilledmovements

Coordinates movement

Medulla oblongata • Has vital centers for breathing, heart rate

Pons • Connects cerebellum, spinal cord

with higher brain centers •

The brain processes and acts on information

Q: Which part of the brain classifies humans as “intelligent” beings?

Limbic System; Involved in emotions

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

Peripheral Nervous SystemPNS Somatic division controls skeletal muscles

controls voluntary movementsIncludes spinal reflexes– Involuntary responses– Does not require conscious

thought

Central N.S.Brain

Spinal cord

Peripheral N.S.

MotorSensory

Autonomic- parasympathetic- sympathetic

Somatic-skeletal muscle-spinal reflexes

Peripheral Nervous SystemPNS Autonomic division:Sympathetic and parasympathetic motor divisions

– Oppose each other– Helps maintain homeostasis– Control functions in cardiac

muscles, glands, smooth muscles, etc.

– Sympathetic stimulates/arouse– Parasympathetic relaxes

Central N.S.Brain

Spinal cord

Peripheral N.S.

MotorSensory

Autonomic- parasympathetic- sympathetic

Somatic-skeletal muscle-spinal reflexes

Sympathetic and parasympathetic motor divisions