Chapter 12 Nervous System

Midbrain

Acts as pathway for impulses between brain and spinal cord.

Cranial nerves

Arise from brain.

Tracts

Bundles of nerve fibers interconnecting different parts of CNS

Brain ventricles

Cavities containing cerebrospinal fluid (CSF).

Central Nervous System (CNS)

Combination of the brain and spinal cord.

Diencephalon

Contains 2 of the most critical areas of the brain: o Thalamus o Hypothalamus

Gyri

Elevated portions of the cerebrum, or convolutions

Subdural space

Empty space between dura mater and arachnoid layer.

Sulci

Fissures, or valleys, between gyri.

Synapse

Point where axon of one neuron meets dendrite of second neuron

Nerve root

Point where nerve is attached to CNS.

Function of CNS

Receives impulses from all over body. Processes this information. Responds with action.

Lobes of Cerebrum

Subdivided into left and right halves called *cerebral hemispheres.*

Neuroligal cells

Variety of cells found in nervous tissue.

Myelin

a fatty substance that acts as insulation for many axons.

Axon

conducts electrical impulse to destination.

Nerve cell body

contains nucleus & organelles.

Dendrites

highly branched projections that receive impulses.

Brain ventricles locations:

o 1 in each cerebral hemisphere. o 1 in thalamus. o 1 in front of cerebellum.

Peripheral Nervous System (PNS) consists of:

o 12 pairs of *cranial nerves.* o 31 pairs of *spinal nerves.*

Efferent neurons

o Also called *motor neurons.* o Carry activity instructions from CNS to muscles or glands.

Afferent neurons

o Also called *sensory neurons.* o Carry sensory information from sensory receptor to CNS.

Nerves of PNS are subdivided into 2 divisions:

o Autonomic nervous system (ANS) o Somatic nerves

Subarachnoid space

o Between arachnoid layer and pia mater. o Contains cerebrospinal fluid.

Central nervous system consists of:

o Brain o Spinal cord

Organs of Nervous System

o Brain o Spinal cord o Nerves

Thalamus

o Center for relaying impulses from eyes, ears, and skin to cerebrum. o Controls perception of pain.

Nervous system is divided into: *Know these 2 abbreviations for exam!*

o Central nervous system (CNS) o Peripheral nervous system (PNS)

4 sections of Brain:

o Cerebrum o Cerebellum o Diencephalon o Brain stem

Neurotransmitter

o Chemical released by axon. o Crosses gap to stimulate dendrite of second neuron.

Hypothalamus

o Controls body temperature, appetite, sleep, sexual desire, and emotions. o Controls autonomic nervous system, cardiovascular system, gastrointestinal system, and release of hormones from pituitary gland.

Functions of Nervous System

o Coordinates and controls body function. o Receives sensory input. o Makes decisions. o Orders body responses.

Peripheral nervous system consists of:

o Cranial nerves o Spinal nerves

Meninges consists of 3 layers:

o Dura mater o Arachnoid layer o Pia mater

4 Lobes of cerebral hemispheres:

o Frontal lobe o Parietal lobe o Occipital lobe o Temporal lobe

Synaptic cleft

o Gap between 2 neurons in a synapse. o Electrical impulse cannot cross.

Neurons

o Individual nerve cells. o Capable of conducting electrical impulses.

Nerve

o Is a bundle of axon fibers located outside CNS. o Carries messages between CNS and various parts of the body.

Temporal lobe

o Left and right lateral portion. o Controls hearing and smell.

Pons

o Means bridge. o Connects cerebellum to rest of brain.

Pia mater

o Means soft mother. o Innermost membrane layer. o Applied directly to surface of brain.

Arachnoid layer

o Means spider-like. o Thin, delicate layer attached to pia mater by web-like filaments.

Dura mater

o Means tough mother. o Outermost, tough, fibrous sac around CNS.

3 Components of Brain stem:

o Midbrain o Pons o Medulla oblongata

Frontal lobe

o Most anterior lobe. o Controls motor function, personality and speech.

Medulla oblongata

o Most inferior portion of brain. o Connects brain to spinal cord.

Occipital lobe

o Most posterior. o Controls vision.

Parietal lobe

o Most superior portion. o Receives & interprets nerve impulses. o Interprets language.

Nervous system composed of 2 types of cells:

o Neurons o Neuroglial cells

Names of most nerves reflect:

o Organ the nerve serves. o Portion of the body the nerve is traveling through.

Cerebral cortex

o Outer layer of cerebrum. o Composed of folds of gray matter.

Coordinates all activity of body by:

o Receives information from both external and internal *sensory receptors.* o Uses that information to adjust activity of *muscles* and *glands* to match needs of body.

Parasympathetic branch

o Serves as counterbalance for sympathetic nerves. o Causes heart rate to slow down, lowers blood pressure, and stimulates digestion.

Spinal nerves

o Split off from spinal cord. o One pair (left and right) exit between each pair of vertebrae.

Sympathetic branch

o Stimulates body in times of stress and crisis. o Increases heart rate, dilates airways, increases blood pressure, inhibits digestion, and stimulates production of adrenaline.

ANS divided into 2 branches:

o Sympathetic branch o Parasympathetic branch

Cerebrum processes:

o Thoughts o Judgment o Memory o Association skills o Ability to discriminate between items.

Brain is the center for:

o Thoughts o Memory o Judgment o Emotion

Cerebrospinal fluid (CSF)

o Watery, clear fluid. o Provides shock protection for CNS.

Peripheral Nervous System (PNS)

the sensory and motor neurons that connect the CNS to the rest of the body

Autonomic Nervous system (ANS)

• Control of involuntary or unconscious bodily functions. • It may increase or decrease the activity of: o Smooth muscle found in viscera and blood vessels. o Cardiac muscle of heart. o Glands.

Neuron

• Each nerve can carry information both to and from CNS. • But any individual neuron can carry information in only one direction.

Cerebrum

• Largest section of the brain • Upper portion

Somatic Nerves

• Mainly involved with conscious and voluntary activities of body. • Serve skin and skeletal muscles. o Carry information from sensory receptors of skin. Such as touch, temperature, pressure and pain. o Carry motor commands to skeletal muscles.

Brain

• One of the largest organs in the body. • Coordinates most body activities.

Meninges

• Protective membrane sac. • Encases entire CNS.

Cerebullum

• Second largest portion of the brain. • Located beneath posterior part of cerebrum. • Aids in: o Coordinating voluntary body movements. o Maintaining balance and equilibrium. • Refines muscular movements initiated in cerebrum.