Lec 5 - Mam Phys

What are the two major divisions of the nervous system?

Central nervous system (CNS) and peripheral nervous system (PNS).

What structures make up the CNS?

The brain and spinal cord.

What structures make up the PNS?

All nerves and ganglia outside the CNS.

What is the primary function of the CNS?

Process, integrate, and coordinate information.

What is the primary function of the PNS?

Transmit information between the body and the CNS.

What are afferent neurons?

Sensory neurons that carry information toward the CNS.

What are efferent neurons?

Motor neurons that carry commands away from the CNS.

What is the mnemonic for afferent neurons?

Afferent Arrives at the CNS.

What is the mnemonic for efferent neurons?

Efferent Exits the CNS.

What are first-order neurons?

Primary sensory neurons that carry information from receptors to the spinal cord or brainstem.

Where are first-order neuron cell bodies located?

Dorsal root ganglia or cranial sensory ganglia.

What are second-order neurons?

Neurons that receive information from first-order neurons and project to the thalamus.

Where are second-order neuron cell bodies located?

The spinal cord or brainstem.

What are third-order neurons?

Neurons that project from the thalamus to the cerebral cortex.

Where are third-order neuron cell bodies located?

The thalamus.

Which neuron is responsible for conscious sensory perception?

The third-order neuron.

What is a sensory receptor?

A specialized structure that detects a stimulus.

What is a sensory pathway?

A chain of neurons carrying sensory information to the brain.

What is decussation?

The crossing of nerve fibers from one side of the nervous system to the other.

Why do most sensory pathways decussate?

So each cerebral hemisphere processes information from the opposite side of the body.

Why do most motor pathways decussate?

So each hemisphere controls the opposite side of the body.

What is the consequence of left hemisphere damage?

It usually affects the right side of the body.

What is gray matter?

Regions containing neuron cell bodies, dendrites, and synapses.

What is white matter?

Regions composed mainly of myelinated axons.

Why is white matter white?

The myelin sheath contains lipid, giving it a pale appearance.

What is a tract?

A bundle of axons within the CNS.

What is a nerve?

A bundle of axons in the PNS.

What is a nucleus in neuroanatomy?

A collection of neuron cell bodies within the CNS.

What is a ganglion?

A collection of neuron cell bodies in the PNS.

What is an ascending tract?

A sensory pathway carrying information toward the brain.

What is a descending tract?

A motor pathway carrying information from the brain.

Which ascending pathway carries fine touch and proprioception?

The dorsal column-medial lemniscus pathway.

Which ascending pathway carries pain and temperature?

The spinothalamic tract.

Where does the dorsal column pathway decussate?

In the medulla.

Where does the spinothalamic tract decussate?

In the spinal cord.

Which pathway carries vibration sense?

The dorsal column-medial lemniscus pathway.

Which pathway carries crude touch?

The spinothalamic tract.

Which pathway carries conscious proprioception?

The dorsal column-medial lemniscus pathway.

What is proprioception?

The awareness of body position and movement.

Which descending tract is most important for voluntary movement?

The corticospinal tract.

Where does the corticospinal tract decussate?

In the medullary pyramids.

What is the motor cortex?

The cerebral cortex responsible for initiating voluntary movement.

What is the somatosensory cortex?

The cerebral cortex responsible for conscious sensation.

In which lobe is the primary motor cortex located?

The frontal lobe.

In which lobe is the primary somatosensory cortex located?

The parietal lobe.

What is the cerebellum responsible for?

Coordination, balance, posture, and motor learning.

Does the cerebellum initiate movement?

No.

What happens if the cerebellum is damaged?

Movements become poorly coordinated (ataxia).

What is ataxia?

A loss of coordinated voluntary movement.

What are the basal nuclei responsible for?

Initiating and regulating voluntary movement.

How do the basal nuclei differ from the cerebellum?

Basal nuclei help initiate movement; the cerebellum fine-tunes movement.

Which disease results from degeneration of dopaminergic neurons affecting the basal nuclei?

Parkinson disease.

Which neurotransmitter is deficient in Parkinson disease?

Dopamine.

What symptoms are common in Parkinson disease?

Tremor, rigidity, bradykinesia, and postural instability.

What is bradykinesia?

Slowness of movement.

Which disease results from degeneration of the caudate nucleus and putamen?

Huntington disease.

What type of movements occur in Huntington disease?

Chorea (rapid, involuntary movements).

What is the thalamus?

The major relay station for sensory information.

Does nearly all sensory information pass through the thalamus?

Yes, except olfaction.

Which sense bypasses the thalamus initially?

Smell (olfaction).

What is the hypothalamus responsible for?

Maintaining homeostasis through autonomic and endocrine regulation.

Name four functions of the hypothalamus.

Temperature regulation, hunger, thirst, hormone control, and circadian rhythms.

What is the brainstem composed of?

Midbrain, pons, and medulla oblongata.

What is the primary function of the medulla?

Control of vital autonomic functions such as breathing and heart rate.

Which part of the brainstem contains the cardiac and respiratory centers?

The medulla oblongata.

What is the reticular formation?

A network of neurons involved in consciousness and alertness.

What happens if the reticular activating system is severely damaged?

Coma may occur.

What are cranial nerves?

Nerves that originate directly from the brain.

How many pairs of cranial nerves are there?

12 pairs.

Which cranial nerves are purely sensory?

I, II, and VIII.

Which cranial nerves are purely motor?

III, IV, VI, XI, and XII.

Which cranial nerves contain both sensory and motor fibers?

V, VII, IX, and X.

What is a reflex?

A rapid, involuntary response to a stimulus.

What are the five components of a reflex arc?

Receptor, sensory neuron, integration center, motor neuron, and effector.

Which neuron enters the spinal cord in a reflex?

The afferent (sensory) neuron.

Which neuron leaves the spinal cord in a reflex?

The efferent (motor) neuron.

What is an interneuron?

A neuron located entirely within the CNS that connects sensory and motor neurons.

Which division of the PNS controls skeletal muscle?

The somatic nervous system.

Which division controls smooth muscle, cardiac muscle, and glands?

The autonomic nervous system.

What are the two divisions of the autonomic nervous system?

Sympathetic and parasympathetic.

Which division is responsible for fight-or-flight responses?

The sympathetic nervous system.

Which division is responsible for rest-and-digest responses?

The parasympathetic nervous system.

What neurotransmitter is released by most sympathetic postganglionic neurons?

Norepinephrine.

What neurotransmitter is released by parasympathetic postganglionic neurons?

Acetylcholine.

Which autonomic division increases heart rate?

The sympathetic nervous system.

Which autonomic division decreases heart rate?

The parasympathetic nervous system.

Which autonomic division dilates the pupils?

The sympathetic nervous system.

Which autonomic division constricts the pupils?

The parasympathetic nervous system.

Which autonomic division stimulates digestion?

The parasympathetic nervous system.

Which autonomic division inhibits digestion?

The sympathetic nervous system.

What is homeostatic integration in the CNS?

The process of coordinating sensory input and motor output to maintain internal stability.