Central Nervous SystemPeripheral Nervous SystemAutonomic Nervous System

Nervous System

The neuron

• Sensory neuron- transmits from sensory receptors to otherneurons

• Motor neuron- transmits impulses from the CNS to muscles or glands

• Relay neuron also called interneuron. Located in the CNS and carry impulses from sensory to motor neurons (as in reflexes)

• Reflex arcs – link the 3 types of neurons

Parts of neuron

• Cell body – contains cytoplasm, nucleus, and organelles• Dendrites - convey signals to cell body• Axon – conducts impulses away from the cell body;

wrapped in Schwann cell layers in an insulating myelin sheath

• Synaptic terminals – tips of axon that release neurotransmitters

• neurotransmitters are the chemicals that cross the synapse to relay an impulse

The Neuron

Central Nervous System

CNS made up of the brain and spinal cordMeninges- protective coveringBrain- gray matter on outside and white matter on insideMajor Regions of Brain:1. cerebrum2. diencephalon3. brain stem (midbrain, pons, and medulla)4. CerebellumCerebrospinal fluid- circulation of hormones, nutrients, and WBC’s in CNS; absorbs shock

Ventricles of the Brain

Cerebrum areas

Cerebral hemispheres• Corpus Callosum- connects left and right hemispheres• Makes up about 83% of the total brain mass • Forms the superior portion of the brain• 3 parts of a hemisphere: cortex, white matter, and basal nuclei

(ganglia)• The surface is covered with ridges called gyri and shallow groves called

sulci• Sulci divide the 5 lobes: frontal, parietal, temporal, occipital, and insula• Larger groves called fissures separate the larger regions

– Longitudinal fissure separates the left and right hemispheres– Transverse cerebral fissure separates the cerebellum from the cerebral

hemispheres

Cerebral hemisphere: general

• Cerebral Cortex– 40% of Brain mass – 10 billion cells arranged in 6

layers– Gray matter is only 2-4 mm thick– 3 kinds of functions: motor, sensory, and

association– Each hemisphere controls the opposite side of the

body, contralateral– Although roughly the same in structure, function

of the two hemispheres is specialized– The cortex works as one unit even though there

are functional areas

3 regions of cortex

Motor- involved in integration of the activities of the skeletal muscles

4 areas of Motor Cortex:1. Primary motor cortex- controls the skeletal movements2. Premotor cotex- controls learned motor skills of a

repetitious or patterned nature, like music, typing, and sports related skills

3. Broca’s area- speech4. Frontal eye field- voluntary movement of eye

Motor cortex and Sensory cortex

3 regions of cortex

Sensory- involved with reception of touch, taste, temperature, and pain

1. Primary somatosensory cortex2. Somatosensory association cortex3. Visual areas- processes signals felayed from sensory neurons of the

eye4. Auditory areas-pitch, loudness, and location of sound5. Olfactory cortex- smell6. Gustatory- taste7. Visceral sensory- conscious perception ex. Upset stomach, full

bladder, need to breath8. Vestibular cortex - equilibrium

3 regions of cortexAssociation – more complex than motor or sensory• This area receives multiple sensory inputs and sends out

multiple motor impulses • The anterior portion is involved in intellect, complex

learning, recall and personality, abstract ideas, judgment, working memory, reasoning, and planning

• Posterior portion (temporal, parietal, and occipital lobes) plays a role in recognizing patterns and faces, as well as putting yourself in perspective with your surroundings. It takes different sensory inputs and synthesizes them into a coherent whole.

Differences between 2 hemispheres

• Left hemisphere is dominant in most people• Damage to right brain results in perceptual

and spatial disorders• Musical ability resides in the right brain• Acquisition of different functions by the 2

sides increases functional capacity of brain, without increasing its size

• Left side is utilized when you compose a sentence, balance a check book, and memorize a list

• Right side is more free-spirited, visual-spatial, intuition, emotion, artistic and musical, poetic and creative

Cerebral White Matter

• Responsible for communication between cerebral areas and the lower CNS

• Consists of myelinated fibers bundeled into large tracts

• Three tracts: commissures, association, and projectioncommissures- connect the hemispheres ( corpus callosum)association- connect the lobes of the cortexprojection- connect the cortex to the rest of the bodys nervous system

2nd region - Diencephalon• Thalamus- largest region of the diencephalon, deep within the brain;

plays a key role in mediating sensation, motor activities, arousal, learning, and memory, “the gateway” to the cerebral cortex.

• Hypothalamus – found below the thalamus it caps the brain stem. The main control center of the body and is vital to overall homeostasis; autonomic control, emotional response, body temp regulation, food intake regulation, regulation of water balance and thirst, sleep-wake cycle, and endocrine function

• Epithalamus- most dorsal portion of the diencephalon, contains the pineal gland which secretes melatonin a sleep-inducing signal and antioxidant. It works with the hypothalamus to regulate the sleep-wake cycle.

Diencephalon

3rd region- Brain Stem

• Made up of the midbrain, pons, and medulla oblangada

• Accounts for only 2.5 % of the total brain mass• Deep gray matter surrounded by white matter• produce the programmed behaviors necessary

for survival• Found between the cerebrum and spinal cord

Brain Stem– Midbrain- • Superior colliculi- visual reflex center, coordinate head and

eye movements• Inferior colliculi- auditory relay from the hearing receptors of

the ear to the sensory cortex, reflex in response to sound (startle)Pons-

– Pons- assist the medulla with breathing, connect brain centers to spinal cord, act as a relay for “conversation”

– Medulla Oblangada- inferior part of the brain stem• Autonomic reflexes maintaining homeostasis• Cardiovascular center• Respiratory center• Vomiting, hiccupping, swallowing, coughing, and sneezing

Brain Stem

4th region- Cerebellum

• Accounts for 11% of the brain mass• Located dorsal to the pons and medulla• Processes inputs received from the cerebral

motor cortex, brain stem, and sensory receptors

• Provides the precise timing and paterns of skeletal contractions for smooth coordinated movements and agility

• Ex driving, typing, and playing an instrument• Occurs subconciously

Spinal Cord

• A two way impulse conduction pathway and reflex center

• Found within the vertebral column• Protected by meninges and cerebrospinal fluid• Thirty one pairs of spinal nerve roots • The cord is enlarged in the cervical and lumbar

regions• Ascending tracts are sensory• Descending tracts are motor

Brain Function• Brain Waves and the EEG- patterns of electrical activity

are called brain waves, a record of this activity is an EEG.– Brain waves are identified by frequency: alpha, beta, theta,

delta– Epilepsy results from abnormal electrical activity causing

involuntary muscle contractions during seizures• Consciousness – scale alertness, drowsiness, stupor, coma – Based on information processing– Fainting is temporary loss of consciousness due to inadequate

supply of blood to the brain– Coma a person is unresponsive to stimuli

Function cont’d• Sleep Wake cycles– Sleep a state of partial consciousness from which one can be aroused,

2 types NREM and REM (rapid eye movement)– REM is closely tied to emotional stability and makes up about 25% of

the sleep cycle– Narcolepsy is involuntary lapses into REM sleep and can occur without

warning• Language- left brain both the Bronca’s and Wernike’s areas

process language, but the Right side controls emotional content• Memory- recall of one’s thoughts, essential to learning and is

part of consciousness, STM and LTM (short and long term)the nature of memory is not completely understood but is closely tied to calcium influx and protein receptors and their binding sites.

Protection of Brain

• Bone, Meninges, and Cerebrospinal fluid play a role in protection of the brain.

• Blood-Brain barrier- the capillaries of the brain are impermeable to water-soluble potentially harmful substances, but allows gases, water, and essential nutrients to move in and out to feed the brain cells

What are the effects of …• Traumatic Brain Injury• Cerebrovascular Accidents• Alzheimer’s disease• Parkinson’s Disease• Huntington’s Disease• Spinal Cord Trauma• Poliomyelitis• ALS – Lou Gehrig’s disease• Cerebral Palsy• Spina bifida cystica or occultta• Psychoses and Neuroses