Nervous System (Pt. 2)

2 major functions of Nerves

1. Irritability

2. Conductivity

Irritability

Response to a stimulus

Conductivity

Transmit impulse to other nerves, muscles or glands

Resting neuron electrical condition

Polarized

Polarized condition of Neuron

more negative ions inside the neuron than outside

Synapse transmission

Neurotransmitter released to cross the synapse to excite adjacent nerve

Synapse transmission step 1

Action potential (AP) reaches axon terminal and electrical charge opens Ca channel

Synapse transmission step 2

Ca cause vesicles containing neurotransmitters to fuse with axon terminal membrane

Synapse transmission step 3

Vesicle opens causing release of neurotransmitter into synaptic cleft

Synapse transmission step 4

Neurotransmitter binds to neurotransmitter receptors on adjacent neuron, initiating previous cycle of Na entry into neuron

Synapse transmission step 5

Neurotransmitter effect is brief as it is removed by diffusion, reuptake into the axon or broken down by enzyme activity

Reflexes

Rapid responses programmed in the body, Predictable and involuntary, Brought by stimulus

Reflex arc involves

CNS and PNS

2 Types of reflexes

1. Somatic (ex. pull hand out of fire)

2. Autonomic (ex. regulation of body functions)

5 Different elements of reflex arc

1. Sensory receptor

2. Sensory neuron

3. Interneuron

4. Motor neuron

5. Effector organ

Sensory receptor

Reacts to stimulus

Sensory neuron

Transmits signal to CNS

Interneuron

Communication center between Afferent and Efferent pathways

Motor neuron

nerve transmitting signal from CNS

Effector organ

muscle/ organ stimulated

Anatomy of brain

1. Divided into two main cerebral hemispheres

2. Hemispheres collectively known as cerebrum

Gyri

Elevated portions of brain

Sulci

1. Shallow grooves of brain

2. Separate gyri

Fissures

1. Deep grooves of brain

2. Separate brain into different lobes

3 Features of brain hemispheres

1. Superficial cortex of grey matter

2. Internal white matter

3. Basal nuclei

Cerebral cortex

Contains areas controlling...

1. Speech

2. Memory

3. Logical and emotional responses

4. consciousness

5. Sensation

6. Voluntary movements

2 Areas of cerebral cortex

1. Primary somatic sensory area

2. Primary motor area

Primary somatic sensory area location

1. Parietal lobe

2. Posterior to central sulcus

Primary motor area location

1. Frontal lobe

2. Anterior to central sulcus

Primary somatic sensory area

1. Interprets all sensory input (excludes special senses)

2. Interprets signals involving threat, temperature, pressure and light touch

3. Sensory signals are crossed (left body corresponds to right brain and vice versa)

Primary motor area

1. Allows person to move body voluntarily

2. Major axons from this region descend to form corticospinal tract

3. Sensory signals are crossed (left body corresponds to right brain and vice versa)

4 Specialized areas of the cortex

1. Broca's area

2. Anterior association area

3. Posterior association area

4. Wernicke's area

Broca's area

1. Found at base of precentral gyrus

2. Anterior to central sulcus

3. Only in left hemisphere

4. Controls speech

Anterior association area

1. Anterior part of frontal lobe

2. Involved with higher intellectual activity and socially acceptable behavior

Posterior association area

1. Encompasses posterior cortex

2. Recognition of patterns and faces

Wernicke's area

1. Posterior cortex

2. Language comprehension

Location of cell body for specialized areas in the cortex

Outermost grey matter

Cerebral white matter

1. Makes up majority of remaining tissue of cortex

2. Impulses are transmitted to, from and within the cortex

3. Large, central fiber tract is the corpus callosum

4. Association fiber tracts

5. Projection fiber tracts

Association fiber tracts

Connect areas within hemispheres

Projection fiber tracts

connect cerebrum with lower CNS

Fiber tract

connects brain hemispheres

Basal nuclei

1. AKA basal ganglia

2. Grey matter deep within white matter

3. Help regulate voluntary motor activities. y modifying instructions

4. Internal capsule passes from basal ganglia to thalamus

Internal capsule

tight band of fibers

Diencephalon location

Top of brain stem

3 Parts of Diencephalon

1. Thalamus

2. Hypothalamus

3. Epithalamus

Thalamus

Relay center for sensory impulses passing into sensory cortex

Hypothalamus

1. Below thalamus

2. Responsible for regulation of temperature, water balance and metabolism

3. Important for emotional drive (appetite, sex, pain, etc.)

4. Member of limbic system

5. Control pituitary gland

2 Hypothalamus hormones

1. Anti-diuretic

2. Oxytocin

Epithalamus

Forms floor of third ventricle

2 Parts of epithalamus

1. Pineal gland

2. Choroid plexus

Pineal gland

1. Part of endocrine system

2. Melatonin

3. Dark/ light cycle

Choroid plexus

Forms CSF

3 Parts of brain stem

1. Mid brain

2. Pons

3. Medulla oblongata

Midbrain

• transmit ascending and descending impulses

corpora quadrigemina

1. Rounded protrusions

2. reflex centers for vision and hearing

cerebral peduncles

Transmit ascending and descending impulses

Cerebral aqueduct

Canal connecting 3rd and 4th ventricles

Pon

1. Below mid brain

2. Made of fiber tracts

3. Contains nuclei involved in breathing

Medulla oblongata

• Contain pyramidal or corticospinal motor tracts, this is the area where they cross over to the opposite site

• Also contains fibers that control visceral activity, HR, BP, breathing, swallowing and vomitting

Reticular formation

1. Extends length of brain stem

2. Made of grey matter

3. Involved in motor control of visceral organs

4. Reticular activation system (RAS) play role in consciousness/ sleep and awake cycle

5. Filters sensory input

6. Damage can result in coma

Cerebellum location

Under occipital lobe of cortex

Cerebellum

Provides timing for muscle activity, balance, and equilibrium, Allows for smooth, fluid and coordinated movement