THE NERVOUS SYSTEM PART 1: PHYSIOLOGY

Neurons (Nerve Cells)

• core communicators between the nervous system

• carry out their functions to their chemical and electrical signals

• working units of the nervous system

• generate and transmit nerve impulses

• transmits information

Neuroglia

• connective tissue formed by glial cells

• supporting cells/tissue that maintains the environment for the function of the neurons

Cell body

• part of the neurons that contains the nucleus, houses dna, where protein is synthesized

Axon

• long, slender projection that transmits signals away from the cell body

Dendrites

• short branching projections that receives signals from other neurons

Nerves

• bundles of axon

Action Potential

• neurons generate and transmit electrical impulses called ______________ which the electrical impulse travels down the axon

Relay stations

• neurons that receive the action potential and pass it along or redirect

Outside the body

• action potential can be initiated in response to stimuli like touch or light waves

Inside the Body

• action potential can be initiated in response to stimuli like a change in the concentration of carbon dioxide in the blood alters respiration or a thought may result in voluntary movement

Cell Body (Soma)

• form the grey matter of the NS and found in the periphery of the brain and in the center of the spinal cord

nuclei

group of cell bodies in CNS

ganglia

group of cell bodies in the PNS

Axons and Dendrites

extensions of cell bodies and form the white matter of the NS

Axons

• found deep in the brain and at the periphery of the spinal cord

• when in a group, it tracts

• each nerve cell has only one

• carry impulses AWAY from the cell body

• longer

• may be myelinated or unmyelinated

axon hillock

a tapered area of the cell body where an axon begins

saltatory conduction

presence of myelin sheath is responsible for ____________________ of action potentials

Node of Ranvier

gaps in the myelin sheath

Dendrites

• short processes that receive and carry incoming action potentials and DIRECT them towards cell bodies

motor neurons

dendrites are part of synapses

sensory neurons

dendrites respond to specific stimuli

Sodium and Potassuim

principal ions involved in action potential (nerve impulse)

faster

a larger diameter of neuron, and myelinated makes the action potential ___________

Resting Potential

neurons maintain the negative charge inside the cell

Depolarization

If the stimulus is successful, the sodium channels will open, causing it to be positive

action potential

When the threshold is reached, it triggers _______ wherein the inside of the cell becomes positively charged

Repolarization

potassium channels open, causing the rush of Na ions out of the cell

Refractory Period

neurons is temporarily unable to reach their action potential, before reaching the resting state

Saltatory conduction

action potential in a myelinated nerve fiber; myelin sheath serves as the insulator to prevent ion breach

Simple propagation

action potential in an unmyelinated nerve fiber; travels along the entire length of the axon as a way of polarization; slower and requires more energy

Synapse

• always more than one neuron involved in the transmission of a nerve impulse from its origin to its destination (sensory/motor)

• no physical contact between two neurons

• point at which the action potential passes from the presynaptic to the postsynaptic neuron

Synaptic Knobs/Terminal Buttons

• at its free end, the axon of the presynaptic neuron breaks up into minute branches that terminate in small swellings called _________________

• in close proximity to the dendrites and the cell body of the postsynaptic neuron

synaptic cleft

• gap/space between the presynaptic and postsynaptic neuron

• where neurotransmitters travel

synaptic vesicles

membrane-bound that stores a chemical neurotransmitter that is released into the synaptic cleft

cell body

where neurotransmitters are produced

neurotransmitters

transported along the axons and stored in the synaptic vesicles

exocytosis

Neurotransmitters are released through _______________________ in response to the action potential and diffuse across the synaptic cleft, where they act on specific receptor sites on the postsynaptic membrane.

enzymes or taken back into the synaptic knob

Their action is short-lived because immediately after they have acted on the postsynaptic membrane, they are either inactivated by _________________________________________________.

mimic, neutralize (antagonize) or prolong

Some important drugs _________________________________________________ the neurotransmitter activity.

excitatory

Neurotransmitters usually have an _____________ effect on postsynaptic receptors but they are sometimes inhibitory.

50

there are more than ____ neurotransmitters in the brain and spinal cord

Astrocytes

TYPES OF NEUROGLIA:

• most abundant

• star-shaped with fine branching processes

• found adjacent to blood vessels, with their foot processes forming a sleeve around them

• blood-brain barrier

blood-brain barrier

selective barrier that protects the brain from toxic subs and chemical variations in the blood

Oligodendrocytes

TYPES OF NEUROGLIA:

• found in clusters round the nerve cell bodies in grey matter

• located adjacent/along the length of myelinated nerve fibers

• form and maintain myelin in CNS

Schwann Cells

TYPES OF NEUROGLIA:

• form and maintain myelin in PNS

Ependymal Cells

TYPES OF NEUROGLIA:

• form the epithelial lining of the ventricles of the brain and central canal of spinal cord

• form the choroid plexuses of the ventricles secrete cerebrospinal fluid

• have cilia that assist the flow of CSF

Microglia

TYPES OF NEUROGLIA:

• smallest and least numerous

• derived from monocytes that migrate from the blood into the NS before birth

• dispersed throughout the brain

• phagocytic

• immune cells

Somatic, Cutaneous, or Common Senses

TYPES OF SENSORY (AFFERENT) NERVES:

• for pain, touch, heat, and cold

Proprioceptor Senses

TYPES OF SENSORY (AFFERENT) NERVES:

• for position of the body and its parts in space thereby enabling maintenance of posture and balance

Special Senses

TYPES OF SENSORY (AFFERENT) NERVES:

• for sight, hearing, balance, smell, and taste

Autonomic Afferent Nerves

TYPES OF SENSORY (AFFERENT) NERVES:

• for involuntary activity and visceral pain

• found in internal organs, glands, and tissues

Somatic Nerves

TYPES OF MOTOR (EFFERENT) NERVES:

• involved in voluntary reflex and reflex muscle coordination

Autonomic Nerves (Sympathetic and Parasympathetic)

TYPES OF MOTOR (EFFERENT) NERVES:

• involved in cardiac and smooth muscle contraction and glandular secretion

• involuntary function

Mixed Nerves

TYPES OF NERVES:

• both sensory and motor in function

Neuroglia (Glial Cells)

have the capacity to reproduce/regenerate

Nuerons

cannot divide

Necrosis

Damage to neurons can lead to rapid ________ with sudden cell death which leads to acute functional failure ce

Atrophy

Damage to neurons can lead to slow _______ with gradually increasing dysfunction

Hypoxia and Anoxia

CAUSES OF NEURON DAMAGE:

• not enough oxygen

Nutritional Deficiencies

CAUSES OF NEURON DAMAGE:

• lack of vitamins

Ageing

CAUSES OF NEURON DAMAGE:

• neurons naturally degenerate

Hypoglycemia

CAUSES OF NEURON DAMAGE:

• low blood sugar can deprive neurons of the energy they need to function

Cerebrum

• largest part of the brain and occupies the anterior and middle cranial fossae

Functions of Cerebrum

3 Main Activities:

• Higher-Order Functions (Language, Memory, Sense of Responsibility, Thinking, Reasoning, Moral Decision Making, and Learning)

• Sensory Perception (Pain, Temperature, Touch, Sight, Hearing, Taste, Smell

• Initiation and Control of Skeletal Muscle Contraction

Frontal Lobe

• Motor Cortex

  • initiates movement

• Prefrontal Cortex

  • thinking

• Broca’s Area

  • language

Temporal Lobe

• auditory cortex

Parietal Lobe

• Somatosensory Cortex

  • sensation and spatial manipulation

Occipital Lobe

• visual cortex

Thalamus

• arousal

• processing of some emotions and complex reflexes

• relays and redistributes impulses from most parts of the brain to the cerebral cortex

• receives information from the sensory and relays that information to the different cortex

• control center in processing information

• located inferior to the cerebrum

Hypothalamus

• situated below and in front of the thalamus, immediately above the pituitary gland

• controls the output of hormones from both anterior and posterior lobes of the pituitary gland

Hypothalamus

FUNCTIONS:

• effectors of the autonomic nervous system

• appetite and satiety

• thirst and water balance

• body temperature

• emotional reactions

• circadian rhythms (sleeping and waking cycles)

Midbrain (Mesencephalon)

• nuclei act as relay stations for the ascending and descending nerve fibers and have important roles in auditory and visual reflexes

• uppermost part of the brain stem

Pons

• located in between the midbrain and the medulla oblongata

• processes information of the cranial nerves

  • controls facial muscles (ex: smiling, frown, chew, and taste)

Pneumotaxic area

• located in the pons

• operates in conjunction with the respiratory center in the medulla oblongata to control respiration

Medulla Oblongata

• vital centers

• nuclei associated with autonomic reflex activity

  • cardiovascular — heart rate and circulation affecting bp

  • respiratory — breathing control

  • reflex centers for omiting, coughing, sneezing, and swallowing

Cerebellum

• referred to as little brain

• controls and coordinates the movements of various groups of skeletal muscle, ensuring smooth, even, and precise actions

• activity is not under voluntary control

• posture, balance, and equilibrium

• language processing

Spinal Cord

• elongated, almost cylindrical part of CNS

• nervous tissue link between the brain and the body

• nerves conveying impulses from the brain to the various organs and tissues descend through the spinal cord

• important for the motor control, sensory input, and reflexes

Peripheral Nervous System

• made up of all nerves, belonging to both the somatic and autonomic nervous systems, entering and leaving the CNS

• its nerves can be sensory, motor, and mixed

spinal nerves

GROUP OF PNS:

• leave the spinal cord through spaces called intervertebral foramina between the vertebrae

Cranial Nerves

GROUP OF PNS:

• originate in the base of the brain and flow out through foramina (tiny holes) in the base of the skull

Cranial Nerves

• 12 pairs

• some are sensory, motor, and mixed

• numbered using Roman numerals according to the order in which they connect to the brain starting anteriorly

Autonomic NS

• controls involuntary body functions

sympathetic

DIVISION OF AUTONOMIC NS:

• thoracolumbar outflow

• fight or flight

• predominates in stressful situations

parasympathetic

DIVISION OF AUTONOMIC NS:

• craniosacral outflow

• rest and digest

• increased in calm and non-stressful situations

decrease

EFFECTS OF AGEING ON NS:

1. As neurons are not replaced after birth, a natural __________ in number occurs with ageing.

2. The brain of older adults are ________ in size and weight.

3. ______________, accumulation of protein material, are often found around CNS neurons and neurofibrillary tangles may develop inside them, although their significance is unknown.

4. Decreased _____________ may develop in the arteries that supply the brain over a long period (atheroma and arteriosclerosis), making their walls more prone to rupture.

5. Motor control of __________ movement diminishes, meaning that they take longer to carry out motor actions and are more prone to falls

6. The conduction rate of nerve impulses becomes _______, contributing to less effective control of vasodilation, vasoconstriction, and the baroreceptor reflex.

7. _________ of the recent past becomes more difficult to access, although long-term memories remain intact.

8. More incapacitated by ______________ changes than others (ex: dementia)

1 = ?

reduced

EFFECTS OF AGEING ON NS:

1. As neurons are not replaced after birth, a natural __________ in number occurs with ageing.

2. The brain of older adults are ________ in size and weight.

3. ______________, accumulation of protein material, are often found around CNS neurons and neurofibrillary tangles may develop inside them, although their significance is unknown.

4. Decreased _____________ may develop in the arteries that supply the brain over a long period (atheroma and arteriosclerosis), making their walls more prone to rupture.

5. Motor control of __________ movement diminishes, meaning that they take longer to carry out motor actions and are more prone to falls

6. The conduction rate of nerve impulses becomes _______, contributing to less effective control of vasodilation, vasoconstriction, and the baroreceptor reflex.

7. _________ of the recent past becomes more difficult to access, although long-term memories remain intact.

8. More incapacitated by ______________ changes than others (ex: dementia)

2 = ?

plaques

EFFECTS OF AGEING ON NS:

1. As neurons are not replaced after birth, a natural __________ in number occurs with ageing.

2. The brain of older adults are ________ in size and weight.

3. ______________, accumulation of protein material, are often found around CNS neurons and neurofibrillary tangles may develop inside them, although their significance is unknown.

4. Decreased _____________ may develop in the arteries that supply the brain over a long period (atheroma and arteriosclerosis), making their walls more prone to rupture.

5. Motor control of __________ movement diminishes, meaning that they take longer to carry out motor actions and are more prone to falls

6. The conduction rate of nerve impulses becomes _______, contributing to less effective control of vasodilation, vasoconstriction, and the baroreceptor reflex.

7. _________ of the recent past becomes more difficult to access, although long-term memories remain intact.

8. More incapacitated by ______________ changes than others (ex: dementia)

3 = ?

blood flow

EFFECTS OF AGEING ON NS:

1. As neurons are not replaced after birth, a natural __________ in number occurs with ageing.

2. The brain of older adults are ________ in size and weight.

3. ______________, accumulation of protein material, are often found around CNS neurons and neurofibrillary tangles may develop inside them, although their significance is unknown.

4. Decreased _____________ may develop in the arteries that supply the brain over a long period (atheroma and arteriosclerosis), making their walls more prone to rupture.

5. Motor control of __________ movement diminishes, meaning that they take longer to carry out motor actions and are more prone to falls

6. The conduction rate of nerve impulses becomes _______, contributing to less effective control of vasodilation, vasoconstriction, and the baroreceptor reflex.

7. _________ of the recent past becomes more difficult to access, although long-term memories remain intact.

8. More incapacitated by ______________ changes than others (ex: dementia)

4 = ?

precise

EFFECTS OF AGEING ON NS:

1. As neurons are not replaced after birth, a natural __________ in number occurs with ageing.

2. The brain of older adults are ________ in size and weight.

3. ______________, accumulation of protein material, are often found around CNS neurons and neurofibrillary tangles may develop inside them, although their significance is unknown.

4. Decreased _____________ may develop in the arteries that supply the brain over a long period (atheroma and arteriosclerosis), making their walls more prone to rupture.

5. Motor control of __________ movement diminishes, meaning that they take longer to carry out motor actions and are more prone to falls

6. The conduction rate of nerve impulses becomes _______, contributing to less effective control of vasodilation, vasoconstriction, and the baroreceptor reflex.

7. _________ of the recent past becomes more difficult to access, although long-term memories remain intact.

8. More incapacitated by ______________ changes than others (ex: dementia)

5 = ?

slower

EFFECTS OF AGEING ON NS:

1. As neurons are not replaced after birth, a natural __________ in number occurs with ageing.

2. The brain of older adults are ________ in size and weight.

3. ______________, accumulation of protein material, are often found around CNS neurons and neurofibrillary tangles may develop inside them, although their significance is unknown.

4. Decreased _____________ may develop in the arteries that supply the brain over a long period (atheroma and arteriosclerosis), making their walls more prone to rupture.

5. Motor control of __________ movement diminishes, meaning that they take longer to carry out motor actions and are more prone to falls

6. The conduction rate of nerve impulses becomes _______, contributing to less effective control of vasodilation, vasoconstriction, and the baroreceptor reflex.

7. _________ of the recent past becomes more difficult to access, although long-term memories remain intact.

8. More incapacitated by ______________ changes than others (ex: dementia)

6 = ?

memory

EFFECTS OF AGEING ON NS:

1. As neurons are not replaced after birth, a natural __________ in number occurs with ageing.

2. The brain of older adults are ________ in size and weight.

3. ______________, accumulation of protein material, are often found around CNS neurons and neurofibrillary tangles may develop inside them, although their significance is unknown.

4. Decreased _____________ may develop in the arteries that supply the brain over a long period (atheroma and arteriosclerosis), making their walls more prone to rupture.

5. Motor control of __________ movement diminishes, meaning that they take longer to carry out motor actions and are more prone to falls

6. The conduction rate of nerve impulses becomes _______, contributing to less effective control of vasodilation, vasoconstriction, and the baroreceptor reflex.

7. _________ of the recent past becomes more difficult to access, although long-term memories remain intact.

8. More incapacitated by ______________ changes than others (ex: dementia)

7 = ?

progressive CNS

EFFECTS OF AGEING ON NS:

1. As neurons are not replaced after birth, a natural __________ in number occurs with ageing.

2. The brain of older adults are ________ in size and weight.

3. ______________, accumulation of protein material, are often found around CNS neurons and neurofibrillary tangles may develop inside them, although their significance is unknown.

4. Decreased _____________ may develop in the arteries that supply the brain over a long period (atheroma and arteriosclerosis), making their walls more prone to rupture.

5. Motor control of __________ movement diminishes, meaning that they take longer to carry out motor actions and are more prone to falls

6. The conduction rate of nerve impulses becomes _______, contributing to less effective control of vasodilation, vasoconstriction, and the baroreceptor reflex.

7. _________ of the recent past becomes more difficult to access, although long-term memories remain intact.

8. More incapacitated by ______________ changes than others (ex: dementia)

8 = ?