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)FOREBRAIN2)MIDBRAIN3)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: