NOTES: CH 49 -

NERVOUS SYSTEM

ORGANIZATION; THE

HUMAN BRAIN

Recall…the nervous system is

divided into 2 divisions:

● CENTRAL NERVOUS SYSTEM (CNS):

information processing; integration

● PERIPHERAL NERVOUS SYSTEM

(PNS): transmits info. to/from the CNS;

plays a large role in regulating an

animal’s movement & internal

environment

Organization of the

CENTRAL NERVOUS SYSTEM:

● consists of the BRAIN & SPINAL

CORD

● BRAIN: integration; complex behavior

● SPINAL CORD: conveys info. to / from

the brain; generates basic patterns of

locomotion

SPINAL CORD:

● can also act independently of the brain

as part of simple nerve circuits:

REFLEXES!

● a reflex protects the body by triggering

a rapid, involuntary response to a

particular stimulus

● EXAMPLE: knee-jerk reflex

Organization of the

CENTRAL NERVOUS SYSTEM:

● CEREBROSPINAL FLUID:

-formed in the brain by filtration of blood

-circulates through brain, providing

nutrients & hormones; carries away

wastes

-cushions the brain & spinal cord

GRAY & WHITE MATTER:

● GRAY MATTER:

-consists mainly of neuron cell bodies,

dendrites, unmyelinated axons, & glia

(support cells)

● WHITE MATTER:

-consists of bundled axons w/myelin

sheaths (gives the white appearance)

Organization of the

PERIPHERAL NERVOUS SYSTEM:

● consists of NERVES that branch out

from the CNS and connect it to other

parts of the body.

● includes:

SPINAL NERVES and CRANIAL

NERVES

CRANIAL NERVES

● mammals have 12 pairs of cranial nerves

● originate from the cerebrum & brain stem

● innervate parts of the head, neck and trunk

CRANIAL NERVES

SPINAL NERVES

● mammals have 31 pairs of

spinal nerves

● originate from the spinal cord

● innervate the upper & lower

limbs, neck, and trunk

SPINAL NERVES

PERIPHERAL NERVOUS

SYSTEM (PNS):

● can be subdivided into the:

1) Motor system: oversees conscious

(voluntary) activities (i.e. skeletal

muscles);

2) Autonomic nervous system: controls

unconscious (involuntary) activities (i.e.

heart, stomach, intestines, glands)

AUTONOMIC NERVOUS

SYSTEM

● branch of the PNS that is involuntary;

● includes 2 subdivisions:

1) SYMPATHETIC DIVISION;

2) PARASYMPATHETIC DIVISION.

● Sympathetic and parasympathetic

divisions may act antagonistically

(in opposition), alternately

activating or inhibiting the actions

of some organs, glands, etc.

SYMPATHETIC DIVISION:

● prepares the body for energy-

expending, stressful, or emergency

situations

EXAMPLE: during an emergency, the

sympathetic division will increase the

heart rate and breathing rate, etc.

PARASYMPATHETIC DIVISION:

● is most active under ordinary, restful

conditions;

● counterbalances the effects of the

sympathetic division

EXAMPLE: after an emergency, the

parasympathetic division decreases the

heart rate, breathing rate, etc.

Parts of the Brain:

● During embryonic development, 3 brain regions become evident:

1) FOREBRAIN

2) MIDBRAIN

3) HINDBRAIN

Brain Regions:

● Forebrain includes: cerebrum, thalamus, hypothalamus

● Midbrain

● Hindbrain includes: pons, medulla oblongata, cerebellum

**the midbrain, along with the pons and medulla oblongata form the BRAINSTEM

BRAINSTEM:

● anterior end of

spinal cord;

● 3 parts that

function in:

-homeostasis

-movement coordination

-conduction of info. to higher

brain centers:

BRAINSTEM:

3 parts of the brainstem:

1) Medulla oblongata

2) Pons

3) Midbrain

1) Medulla oblongata: controls breathing,

heart and blood vessel activity / dilation (and

therefore blood pressure), respiratory

center, swallowing, vomiting, digestion

2) Pons: regulates

breathing centers in

the medulla; relays

impulses between the

cerebrum and the

medulla, and the

cerebrum and

cerebellum.

3) Midbrain:

● receives and sends sensory information;

● coordinates visual reflexes (eye

movements with other movements)

● coordinates auditory reflexes (move the

head to hear a sound more distinctly)

CEREBELLUM:

● coordination of movement;

● balance;

● hand-eye coordination

THALAMUS:

● relay center that sorts out & transmits

sensory information to and from cerebrum;

● incoming information from all the senses is

sorted here and sent on to the appropriate

higher brain center;

● involved in regulating emotion

& arousal (wakefulness)

HYPOTHALAMUS:

important regulator of HOMEOSTASIS

contains body’s thermostat

includes centers for regulating hunger &

thirst

plays role in sexual response and

mating behavior

HYPOTHALAMUS:

fight-or-flight response, pleasure, daily

biorhythms (“biological clock”)

source of posterior pituitary hormones &

releasing hormones for anterior pituitary

hormones

CEREBRUM:

divided into hemispheres (R and L)

each hemisphere divided into lobes

(frontal, parietal, temporal, occipital)

each hemisphere has an outer covering

of gray matter = CEREBRAL CORTEX

hemispheres are connected by white

matter called CORPUS CALLOSUM

CEREBRUM – functions!

where memories are stored

interprets sensory impulses arriving

from sense organs

centers for motor coordination; send motor

impulses to muscles

where conscious decisions are made

intelligence and personality stem from

cerebral activity

language, cognition / thought / problem

solving

There are 2 functional cortical areas:

1) Primary Motor Cortex: sends commands

to skeletal muscles, signaling appropriate

responses to sensory stimuli

2) Primary Somatosensory Cortex:

receives and integrates signals from

touch, pain, pressure, and temperature

receptors;

divided into specific areas so that we

can associate specific stimuli with

specific parts of the body.

Nervous System Disorders:

● Schizophrenia

● Depression

● Bipolar disorder (manic-depressive)

● Drug addiction

● Alzheimer’s Disease

● Parkinson’s Disease

Schizophrenia:

Drug

Addiction:

The power of the brain!

• LINK to video of paraplegic

patients regaining some

sensation / mobility in

paralyzed limbs…!