COMPENDIUM REVIEW # 1 FOR UNIT # 3

TABLE OF CONTENTS
CHAPTER 13

NERVOUS SYSTEM

1. Overview of the Nervous System
a. Nervous tissue
b. Neuron structure
c. Myelin sheath
d. Propagation of an action potential
f. Synapse
2. Central Nervous System
a. Spinal cord
b. The brain
3. Limbic System and Higher Mental Functions
a. Limbic system
b. Higher mental funtions
4. The Peripheral Nervous System
a. Somatic system
b. Autonomic system
c. Somatic versus the autonomic system
5. Drug Abuse
a. Alcohol
b. Nicotine
c. Cocaine
d. Methamphetamine
e. Heroin
f. Marijuana
CHAPTER 14
SENSES
6. Sensory Receptors and Sensations
a. Types of sensory receptors
b. How sensations occurs
7. Proprioceprors and Cutaneous Receptors
a. Proprioceptors
b. Cutaneous receptors
c. pain receptors
8. Senses of Taste and Smell
a. Sense of taste
b. Sense of smell
9. Sense of Vision
a. Anatomy and physiology of the eye
b. Abnormalities of the eye
10. Sense of Hearing
a. Anatomy and physiology of the ear
11. Sense of Equilbrium
a. Rotational equilibrium pathway
b. Gravitational equilibrium pathway


CHAPTER 13

OVERVIEW OF THE NERVOUS SYSTEM

The nervous system is divided into the central nervous system(CNS) and the peripheral nervous system(PNS). It has 3 functions: 1. reception and input, 2. integration of data, 3. generates motor input.
Nervous tissue contains 2 types of cells: neurons and neuroglia. Neurons transmit nerve impulses and Neuroglia nourish and support neurons.

A neuron is composed of dendrites, a cell body and an axon. There are 3 types of neurons: 1. Sensory neurons which take nerve impulses form sensory receptors to the CNS. 2. Interneurons occur within the CNS and 3. Motor neurons take nerve impulses from the CNS to effectors.

See illustration.*

The myelin sheath is the covering over long axons.

Nerve impulse includes resting potential and action potential. Resting potential is more sodium ions (Na+) outside the axon and more potassium (K+) inside the axon. The axon does not conduct and impulse.

Action potential is a change in polarity across the axonal membrane as a nerve impulse occurs: when Na+ gates open, Na+ moves to the inside of the axon, and depolarization occurs. When K+ gates open and K+ moves to outside the axon, a repolarization occurs. See illustration.*

A synapse is junction between neurons consisting of the presynaptic (axon) membrane, the synaptic cleft, and postsynaptic (usually dendrite) membrane.

When a neurotransmitter is released into a synaptic cleft, transmission of a nerve impulse occurs.

Neurotransmitter binds to receptors in receiving membrane and causes excitation or inhibition.

Integration is the summing of excitatory and inhibitory signals.

See illustration.*

THE CENTRAL NERVOUS SYSTEM

The CNS receives and integrates sensory input and formulates motor output. The CNS consists of the spinal cord and brain.
The spinal cord is the nerve cord that is continuous with the base of the brain plus the vertebral column that protects the nerve cord.
A cross section of the spinal cord shows a central canal, gray matter and white matter. Gray matter contains neuron cell bodies. White matter consists of myelinated axons that occur in tracts.

It conducts to and from the brain and carries out reflex actions.

The brain has 4 major parts, the cerebrum, the diencephalon, the cerebellum and the brain stem. It also has 4 ventricles, 2 lateral ventricals, the 3rd ventrical and the 4th ventrical.

See illustration.*

The cerebrum has two cerebral hemispheres connected by the corpus callosum. Sensation, reasoning, learning and memory, and language and speech take place in the cerebrum. the cerebral cortex covers the cerebrum. The cerebral cortex of each cerebral hemisphere has four lobes: frontal, parietal, occipital, and temporal.

The frontal lobe sends out motor commands to lower brain centers, which pass them on to motor neurons. The parietal lobe receives sensory information from lower brain centers in communication with sensory neurons. Association areas are located in all lobes.

See illustration.*

The Diencephalon includes the hypothalmus which controls homeostasis. the thalamus sends sensory input on to the cerebrum.

The cerebellum coordinates skeletal muscle contractions.

The brain stem, the medulla oblongata and the pons have centers for breathing and the heartbeat.

THE LIMBIC SYSTEM AND HIGHER MENTAL FUNCTIONS

The limbic system, which lies deep in the brain, is involved in determining emotions.
The amygdala determines when a situation deserves the emotion we call "fear."
The hippocampus is particularly involved in storing and retrieving memories.

THE PERIPHERAL NERVOUS SYSTEM

The PNS only contains only nerves and ganglia. Cranial nerves take impulses to and from the brain. Spinal nerves take impulses to and from the spinal cord. The PNS is divided into the somatic systema and autonomic system.

The somatic system serves the skin, skeletal muscles, and tendons. Some actions are due to reflexes, which are automatic and involuntary. Other actions are voluntary, and originate in the cerebral cortex.
The autonomic system is divided into 2 divisions which are sympathetic division and the parasympathetic division. The Sympathetic Division are responses that occur during times of stress. The Parasympathetic Division are responses that occur during times of relaxation. The actions in these divisions are involuntary and automatic. These divisions also innervate internal organs. There are two neurons and one ganglion are utilized for each impulse.

See illustration.*

DRUG ABUSE

Drugs that are commonly abused include alcohol, nicotine, cocaine, methamphetamine, heroin and marijuana.
The effects of alcohol and heroin on the CNS is a depressant. Nicotine, cocaine, and methamphetamine all acts as a stimulant. Marijuana acts as a psychoactive, it creates a euphoria.

CHAPTER 14

SENSES

SENSORY RECEPTORS AND SENSATIONS

There are 4 types of sensory receptors: chemoreceptors ( taste and smell), photoreceptors (vision), mechanoreceptors ( hearing, rotational and gravitational equilibrium) , and thermoreceptors(located in hypothalamus and skin).

Sensory receptors initiate nerve impulses that are transmitted to the spinal cord and/or brain.

Sensation occurs when nerve impulses reach the cerebral cortex. Perception is an interpretation of sensations.

See illustration.*

PROPRIOCEPTORS AND CUTANEOUS RECEPTORS

Proprioceptors are mechanoreceptors involved in reflex actions and help maintain equilibrium and posture.

Cutaneous receptors are found in the skin and are for touch, pressure, temperature, and pain.

SENSES OF TASTE AND SMELL

Taste and smell are chemoreceptors. They are stimulated by molecules in the environment.

Sense of taste: Microvilli of taste cells have receptor proteins for molecules that cause the brain to distinguish sweet, sour, salty, and bitter tastes.

Sense of smell: The cilia of olfactory cells have receptor proteins for molecules that cause the brain to distinguish odors.

SENSE OF VISION

Vision depends on the eye, the optic nerve, and the visual areas of the cerebral cortex.

The eye has 3 layers. The sclera ( outer layer), the choroid ( middle layer), and the retina ( inner layer).

See illustration for the in depth anatomy of the eye.*

In this illustration it gives the parts of the eye and what it does.*

The lens of the eye brings the light rays to focus on the retina. To see a close object, visual accommodation occurs as the lens rounds up.
The visual pathway to the brain begins when light strikes photorecptors in the retina. The optic nerves carry nerve impulses from the eyes to the optic chiasma, then pass through the thalamus before reaching the primary vision area in the occipital lobe of the brain.

Some abnormalities of the eye are color blindness and a misshapen eyeball.

SENSE OF HEARING

Hearing depends on the ear, the cochlear nerve and the auditory areas of the cerebral cortex.

This illustration gives all the parts of the ear.*

The ear has 3 parts. In the outer ear, the pinna and the auditory canal direct sound waves to the middle ear. In the middle ear, the tympanic membrane and ossicles amplify sound waves. In the inner ear, the semicircular canals detect rotational equilibrium; the utricle and saccule detect gravitational equilibrium; and the cochlea houses the spiral organ, which contains mechanoreceptors for hearing.

Auditory pathway to the brain begins when the outer ear receives and the middle ear amplifies sound waves that then strike the oval window membrane.

The mechanoreceptors for hearing are hair cells on the basilar membrane of the spiral organ. Nerve impulses begin in the cochlear nerve and are carried to the primary auditory area in the temporal lobe of the cerebral cortex.

SENSE OF EQUILIBRIUM

The ear also contains mechanoreceptors for equilibrium.

Rotational equilibrium pathway is when the hair cells in the semicircular canals detect rotational and/or angular movement of the head.

Gravitational equilibrium Pathway is when the hair cells in the utricle and saccule detect head movement in the vertical or horizontal planes.

*http://highered.mcgraw-hill.com/classware/selfstudy.do?isbn=0072986867