Exam 5 A&P - IUN P261

Where does the adult spinal cord arise from?

The brainstem at the foramen magnum of the skull.

What is the length of the adult spinal cord?

It ends between L1 and L2.

How many pairs of spinal nerves does the spinal cord give?

31 pairs.

What are the longitudinal grooves on the spinal cord called?

The anterior median fissure and posterior median sulcus.

What are the regions of the spinal cord?

Cervical, thoracic, lumbar, and sacral regions.

What is the cervical enlargement?

A thicker region of the spinal cord from C3 to T1 that provides nerves to the upper limbs.

What is the lumbosacral enlargement?

A region from T12 to L1 that provides nerves to the pelvic region and lower limbs.

What is the conus medullaris?

The tapered conical portion of the spinal cord below the lumbar enlargement.

What is the filum terminale?

A fibrous tissue that supports the spinal cord and anchors it to the coccyx.

What is the function of the posterior median sulcus?

It divides the spinal cord into right and left halves.

What is the role of the anterior median fissure?

It incompletely divides the spinal cord into two symmetrical halves.

What are the three layers of the spinal meninges?

Dura mater, arachnoid, and pia mater.

What is contained in the subarachnoid space?

Cerebrospinal fluid (CSF).

What is the difference between gray matter and white matter in the spinal cord?

Gray matter contains cell bodies and dendrites, while white matter consists of axon bundles.

What are the gray horns in the spinal cord?

Projections of gray matter toward the outer surface of the cord.

What do the posterior (dorsal) gray horns contain?

Somatic and visceral sensory neurons.

What do the anterior (ventral) gray horns contain?

Somatic motor neurons.

What are ascending tracts in the spinal cord responsible for?

Carrying sensory information from the spinal cord to the brain.

What do descending tracts do?

Carry motor information from the brain to the spinal cord.

What is the function of first order neurons in sensory pathways?

They detect stimuli and conduct signals to the spinal cord or brainstem.

What is the role of second order neurons in sensory pathways?

They continue the signal to the thalamus.

What do third order neurons do?

They carry the signal to the cerebral cortex.

What is the function of upper motor neurons?

They begin in the cerebral cortex or brainstem and terminate in lower motor neurons.

What is the role of lower motor neurons?

They send axons to skeletal muscles to cause contraction.

What is the posterior column pathway responsible for?

Carrying fine touch, pressure, and proprioceptive sensations.

What sensations does the anterolateral pathway carry?

Poorly localized sensations of crude touch, pressure, pain, itch, and temperature.

What do spinocerebellar pathways carry?

Sensation to the cerebellum concerning proprioception.

What is the significance of decussation in sensory pathways?

It means that sensory information from one side of the body is processed by the opposite side of the brain.

What are the three somatic motor pathways?

Corticospinal & cortical bulbar pathway, medial pathways, lateral pathways.

What role do the basal nuclei and cerebellum play in somatic motor pathways?

They monitor and adjust activity within these pathways, facilitating or inhibiting neurons.

What is the function of the corticospinal pathway?

It carries motor signals from the cerebral cortex to the brainstem and spinal cord for fine, skilled movements.

Where do corticobulbar tracts terminate?

At cranial nerve nuclei controlling jaw, eye, face, and some neck muscles.

What is the primary role of the extrapyramidal system?

To issue motor commands as a result of subconscious processing, regulating and coordinating involuntary movements.

What are the upper motor units in the brainstem?

Vestibular nuclei, superior and inferior colliculi, red nucleus, and reticular formation.

What is a nerve plexus?

A complex interwoven network of nerves from different spinal nerves made of mixed nerves.

What is the function of the cervical plexus?

It innervates the muscles and skin of the head, neck, and shoulders.

What is a dermatome?

An area of skin innervated by a single spinal nerve root.

How can doctors assess spinal nerve damage?

By testing dermatomes with pinpricks to note areas without sensation.

What are reflexes?

Rapid automatic responses to stimuli involving sensory and motor fibers.

What are the five steps of a reflex arc?

1. Arrival of stimulus and activation of receptor; 2. Activation of sensory neuron; 3. Integration; 4. Activation of motor neuron; 5. Response by effector.

What distinguishes innate reflexes from acquired reflexes?

Innate reflexes result from connections formed during development, while acquired reflexes are learned.

What is the difference between cranial and spinal reflexes?

Cranial reflexes are processed in the brain, while spinal reflexes occur in the spinal cord.

What are somatic reflexes?

Reflexes that control skeletal muscle and provide rapid responses.

What are visceral reflexes?

Reflexes that control activities of other systems, such as blood pressure and urination.

What is a monosynaptic reflex?

A reflex where a sensory neuron synapses directly on a motor neuron without an interneuron.

What is a polysynaptic reflex?

A reflex that involves at least one interneuron between the sensory and motor neurons.

What is the patellar reflex?

A stretch reflex that monitors skeletal muscle length and tone.

What are muscle spindles?

Specialized sensory receptors located within skeletal muscles that help maintain muscle tone and posture.

What is the role of tendon organs?

To prevent excessive tension on tendons by producing sudden relaxation of the contracting muscle.

What is the flexor (withdrawal) reflex?

A quick contraction of flexor muscles resulting in the withdrawal of a limb from injurious stimuli.

What is the crossed extension reflex?

A withdrawal reflex where a painful stimulus to one limb causes that limb to flex and the opposite limb to extend.

Brain

Covered by the same meninges (Dura, arachnoid and pia mater) as the spinal cord.

Forebrain

Most prominent part is cerebrum, responsible for thought, emotions, and memory.

Gyri

Ridges on the brain.

Sulci

Grooves or fissures on the brain.

Diencephalon

Surrounded by the cerebrum, includes thalamus and hypothalamus.

Thalamus

Major relay station to the cerebral cortex for sensory information.

Hypothalamus

Controls emotions, autonomic functions, and hormone production.

Cerebellum

Involved in motor control.

Brainstem

Includes midbrain, pons, and medulla oblongata.

Midbrain

Connects hindbrain and forebrain, involved in auditory and visual processing.

Pons

Involved in somatic and visceral motor control.

Medulla Oblongata

Controls autonomic functions like breathing and heart rate.

Cerebrospinal Fluid (CSF)

Fills the ventricles of the brain.

Cerebellar Damage Signs

Include poor balance, coordination issues, tremors, and dysarthria.

Cerebral Cortex

Involved in higher brain functions including voluntary motor function and sensory processing.

Frontal Lobe

Responsible for voluntary motor function, motivation, and aggression.

Parietal Lobe

Involved in reception and evaluation of sensory information except smell, hearing, and vision.

Occipital Lobe

Responsible for reception and integration of visual input.

Temporal Lobe

Involved in smell and hearing, memory, and judgment.

Limbic System

Center of emotion and learning, includes cingulate gyrus, hippocampus, and amygdala.

Cranial Nerves

12 pairs that communicate between the brain and the rest of the body.

Olfactory Nerve (I)

Responsible for the sense of smell.

Optic Nerve (II)

Carries visual information from the eyes.

Oculomotor Nerve (III)

Innervates extraocular muscles and controls pupil size.

Trigeminal Nerve (V)

Mixed nerve responsible for sensation in the face and controlling chewing muscles.

Facial Nerve (VII)

Controls muscles of the face and scalp, and provides taste sensations.

Vestibulocochlear Nerve (VIII)

Monitors balance and hearing.

Glossopharyngeal Nerve (IX)

Innervates the tongue and pharynx, controls swallowing.

Vagus Nerve (X)

Widely distributed to internal organs, vital for autonomic control.

Accessory Nerve (XI)

Innervates muscles associated with neck and shoulder.

Hypoglossal Nerve (XII)

Controls movement of the tongue.

What is the primary function of the Autonomic Nervous System (ANS)?

Coordinates cardiovascular, respiratory, digestive, urinary, and reproductive functions.

How does the ANS operate in relation to the conscious mind?

Works without instructions or interference from the conscious mind.

What are the two main divisions of the ANS?

Sympathetic division and Parasympathetic division.

What is the sympathetic division often referred to as?

The 'fight or flight' system.

Where do the preganglionic fibers of the sympathetic division originate?

From the thoracic and lumbar segments of the spinal cord.

What is the parasympathetic division often referred to as?

The 'rest and repose' system.

Where do the preganglionic fibers of the parasympathetic division originate?

From the brain and sacral segments of the spinal cord.

What is the enteric nervous system?

A nerve network in the walls of the digestive tract.

What is the anatomy of the sympathetic division?

Preganglionic neurons are in the lateral horns between segments T1 and L2; ganglionic neurons are in sympathetic ganglia near the vertebral column.

What are the three types of sympathetic ganglia?

Sympathetic chain ganglia, collateral ganglia, and adrenal medulla.

What do the celiac ganglion innervate?

Stomach, liver, gall bladder, pancreas, spleen, and part of the small intestine.

What is the role of the adrenal medulla in the sympathetic system?

It acts as a modified sympathetic ganglion that secretes epinephrine and norepinephrine.

What is the primary neurotransmitter released by preganglionic fibers in the sympathetic division?

Acetylcholine (ACh).

What neurotransmitter do most postganglionic fibers in the sympathetic division release?

Norepinephrine (NE).

What are varicosities in the context of sympathetic neurotransmission?

They are swellings along adrenergic fibers that release neurotransmitters.

What are the two types of adrenergic receptors?

Alpha receptors and Beta receptors.

What is the effect of alpha-1 adrenergic receptors?

They release Ca2+ and are found in vascular smooth muscle.

What is the primary function of beta-2 adrenergic receptors?

They cause relaxation of respiratory smooth muscle and are found on many blood vessels.