Neuro: Introduction

Question 1

The nervous system

Answer 1

The body’s communication and control network (it receives, processes, and communicates information)

Divided into:

1. Central nervous system (CNS): brain and spinal cord
2. Peripheral nervous system (PNS): cranial nerves and spinal nerves

Question 2

CNS

Answer 2

Processes, interprets, and stores information; issues orders to muscles, glands, and organs

Consists of:

1. Brain
2. Spinal cord (bridge between brain and peripheral nerves)

Question 3

PNS

Answer 3

Transmits information to and from the CNS

Further divided into:

1. Somatic nervous system: VOLUNTARY control of skeletal muscles
2. Automatic nervous system (ANS): INVOLUNTARY regulation of glands, blood vessels, and internal organs

Subdivisions of ANS:

1. Sympathetic nervous system (SNS): mobilizes body for action (energy output)
2. Parasympathetic nervous system: maintains quiet state (conserves energy)

Question 4

Nervous system cells

Answer 4

Types of cells:
1. Neuron: primary information and communication cell that uses glucose for energy; Consists of: (1) Soma (cell body), (2) dendrites (extension that carry impulses toward the soma), and (3) axons (long projections that carry impulses away from soma)

2. Neuroglial cells: non-conducting cells; Function: Provide support, protection, and nutrition for neurons (i.e. Schwann cells make myelin sheath that surrounds axons); Types: Astrocytes, microglia and oligodendrocytes in CNS; Schwann and satellite cells in PNS

Question 5

Conduction velocity

Answer 5

Dependent on myelin sheath and axon diameter

Fast conduction = Presence of myelin and large axon diameter

Question 6

Types of Neurons

Answer 6

Structures: Multipolar (multiple dendrites), bipolar (one dendrite, one axon), and pseudo-unipolar (no dendrites)

Types:
1. MOTOR neurons: transmit impulses away from the CNS to effector organs

2. ASSOCIATION neurons: transmit impulses between neurons in the CNS
3. SENSORY neurons: transmit impulses from peripheral sensory receptors to the CNS

Question 7

Nerve injury and regeneration

Answer 7

CNS injury = PERMANENT loss of damaged neurons

Peripheral nerve injury = AXONAL REACTION (repair themselves; slowly, ~1 mm. per day)

Question 8

Nerve impulse

Answer 8

Neurons generate and conduct electrical and chemical impulses, and influence other nearby neurons by the release of chemicals (neurotransmitters)

APs are generated and conducted along the neuron when the membrane potential is raised sufficiently (all-or-nothing response)

Question 9

Synapses

Answer 9

Regions between adjacent neurons that allow transmutation of impulses by chemical and electrical conduction

Neuroplasticity: brain synapses can change in strength and number through life

Types of synapses between presynaptic (toward synapse) and postsynaptic neurons (away from synapse):

1. Axoaxonic: between axons
2. Axosomatic: axon to cell body
3. Axodendritic: axon to dendrite
4. Dendrodendritic: dendrite to dendrite

Question 10

Synapse pathway

Answer 10

1. Arrival of AP at synapse
2. Vesicles containing neurotransmitters on presynaptic neuron release their contents into the synaptic cleft
3. Neurotransmitters bind to specific receptors on postsynaptic neuron
4. Trigger AP on postsynaptic neuron

Question 11

Neurotransmitters

Answer 11

More than 46 types (i.e. Norepinephrine, acetylcholine, dopamine, histamine, GABBA, serotonin)

i.e. Myasthenia gravis: dysfunction of acetylcholine (prevents muscle contraction)

Effects on postsynaptic neurons:

1. Excitatory (depolarization)
2. Inhibitory (hyperpolarization)

Question 12

Brain

Answer 12

Lobes: Frontal, parietal, occipital, and temporal

Major divisions:

1. Forebrain
2. Midbrain
3. Hindbrain

Question 13

Forebrain

Answer 13

Consists of:
1. Cerebral cortex: includes all four lobes, gyri (folds), and sulci (space between folds); made up of grey matter (which integrates, stores, and transmits information) and white matter (myelinated neurons); Controls: Thoughts, behavior, memory, motor, sensory, vision, speech, and hearing

2. Basal ganglia: lays deep inside the cerebral cortex; responsible for control of voluntary movements, cognitive and emotional functions
3. Thalamus and hypothalamus: controls many functions including hormone synthesis and temp. regulation

Question 14

Midbrain

Answer 14

Connects forebrain with hindbrain

Functions:

1. Eye movements
2. Movements related to hearing
3. Site of dopamine synthesis (dysfunction is associated with Parkinson’s and schizophrenia)
4. Cerebral aqueduct: transmits CSF (obstruction is a common cause of hydrocephalus)

Question 15

Hindbrain

Answer 15

Consists of:
1. Cerebellum: controls involuntary movements, posture, and balance

2. Pons: transmit information from cerebellum to brainstem (contains multiple CN nuclei)
3. Medulla: controls reflexes such as HR, resp., BP, sneezing, coughing, vomiting, swallowing (contains other CN nuclei)

Question 16

Brainstem

Answer 16

Made up of midbrain, pons, and medulla; connects the cerebral hemispheres, cerebellum, and the spinal cord

Reticular activating system: essential for wakefulness and attention (cells in this system control vital functions such as breathing and HR)

Question 17

Perivascular spaces in the brain

Answer 17

Spaces:
1. EPIDURAL: Between skull and dura

2. SUBDURAL: Between dura and arachnoid matter
3. SUBARACHNOID: Between arachnoid and pia matter (contains CSF)

Question 18

CSF

Answer 18

Produced by the choroid plexuses in the lateral, 3rd and 4th ventricles (midbrain); and is reabsorbed through the arachnoid villi

Anatomy and physiology of CSF:

1. Circulates between 125-150 mL in the ventricles
2. Contains glucose, protein, albumin, electrolytes, pH 7.3 (provides nutrients)
3. Exerts pressure within the brain and spinal cord to prevent damage to the meninges, nerve roots, and blood vessels (in case of impact)

Question 19

Spinal cord

Answer 19

Protected by the vertebral column (within the vertebral canal); it originates at the medulla and ends at conus medullaris in the lumbar spine

Transmits long motor and sensory impulses that originate in the brain; controlls some somatic and automatic reflexes

Question 20

PNS structures

Answer 20

Structures:
1. Cranial nerves: specialized sensory functions (smell, sight, taste, hearing)

2. Spinal nerves
3. Peripheral nerves: ASCENDING (afferent pathways carry sensory information to the CNS) and DESCENDING (efferent pathways go to organs)

Question 21

Somatic nervous system

Answer 21

Motor and sensory pathways that regulate VOLUNTARY motor control of skeletal muscle and sensory information

Question 22

ANS

Answer 22

Motor and sensory pathways that regulate the body’s internal environment through the INVOLUNTARY control of organ systems (coordinates and maintains a steady state among the visceral organs)

Divisions: SNS and parasympathetic nervous system

Neurons: Preganglionic (myelinated) and postganglionic (unmyelinated)

Question 23

SNS

Answer 23

“Fight-or-flight” functions:

1. Mobilizes energy
2. Decreases peristalsis
3. Increases glucose release, temp., and BP
4. Regulates vasomotor tone

Sympathetic activation result in:
1. Adrenal medulla activation: release of epinephrine and norepinephrine (increased strength of heart contractions)

2. Contraction of arteriolar smooth muscles (vasoconstriction): increased peripheral resistance (and increased BP)
3. Bronchodilation (increased oxygenation)

Question 24

Parasympathetic nervous system

Answer 24

“Rest and repose” functions:

1. Decreases HR
2. Promotes digestion
3. Increases salivary secretions
4. Contracts the bladder