Chapter 13-15

Exam 5

pairs of spinal nerves

31

gross anatomy of spinal cord

1) cervical enlargement: C3-T1- upper limbs

2) lumbosacral enlargement: T12-L1- lower limbs; pelvic region

3) conus medullaris- tapered, conical end of the spinal cord (L1-L2)

4) filum terminale- thin strand fibrous tissue; extends fromt he conus medellaris; anchors spinal cord- coccyx

Number of pairs for nerves

1) cervical - 8 pairs

2) thoracic - 12 pairs

3) lumbar- 5 pairs

4) sacral- 5 pairs

5) coccygeal nerves- 1 pair

denticulate ligaments

extend from pia to dura mater

nuclei

cluster of neuron cell bodies in gray matter of the brain or spinal cord

gnaglia

cluster of neuron cell bodies outside the CNS

posterior (dorsal) gray horn

contains somatic and visceral SENSORY neurons

anterior (ventral) gray horn

contains somatic MOTOR neurons

lateral gray horn

contains visceral MOTOR neurons

gray commisure

contains axons that cross from one side to another

white matters

divided into columns (funiculi)

ascending tracts

carry sensory info to the brain

3 neurons:

1) first order- detects stimuli and conducts a signal to the spinal cord or brainstem

2) second order- continues as far as a gateway to the thalamus

3) third order- carries the signal the rest of the way to the cerebral cortex

contralateral

all tracts going to and from the cerebral cortex decussate before reaching the thalamus

ipsilateral

origin and destination same side of the body

descending tracts

1) upper motor neuron- begins with a cell body in the cerebral cortex and has an axon that terminates in lower motor neuron in the brain stem or spinal cord 

2) lower motor neuron- axons of the lower motor neuron then leads the rest of the way to the muscle or other target organ

crossover

axon of the second order neuron will decussate

somatic sensory pathways

paired set of tracts on both side of the spinal cord

1) posterior (dorsal) column pathway —visceral pain

a) fasciculus gracilus- carry info from inferior portion of the body lower trunk and limbs

b) fasciculus cuneatus- superior portion; upper limbs and neck

2) anterolateral pathways *spinothalamic and others)

3) spinocerebellar pathways

posterior column pathway (dorsal column/ medial lemiscus pathway)

carries fine touch, pressure, and proprioceptive sensations

a) fasciculus gracilus- carry info from inferior portion of the body lower trunk and limbs

b) fasciculus cuneatus- superior portion; upper limbs and neck

second order neurons in the nucleus gracilis or nucles cueatus within the medulla

info to thalamus through medial leminscus

anterolateral pathway

carries poorly localized sensation; temp, itch, pain

second order neurons- posterior gray horn of the spinal cord and decussate in the spinal cord 

ascend within the anterior and lateral spinothalamic tracts (also the spinoreticular and spinomesencephlic tracts)

spinocerebellar pathway

carries sensation to the cerebellum;

proprioception

second order neurons in the spinal cord

1) posterior spinocerebellar tracts- uncrossed axons; enter cerebellum via inferior peduncle

2) anterior spinocerebellar tracts- mostl crossed but some uncrossed; most crosses axons re cross

somatic motor pathway neurons

1) upper motor neurons- cell body lies in a CNS processing center

2) lower motor neuron- cell body located in a motor nucleus of the brain or spinal cord and send axons to skeletal muscles

each lower motor neuron innervates a single motor unit an cause contraction of a muscle

somatic motor pathways

1) corticospinal and cortical bulbar pathway

2) medial pathways

3) lateral pathways

basal nuclei (group of subcortical structures) and cerebellum monitor and adjust activity within these pathways; facilitate or inhibit neurons 

corticospinal pathway

aka: pyramidal system: carry motor signals from the cerebral cortex of the brainstem and spinal cord

The adult spinal cord arises from the brainstem at the $\text{foramen}$ $\text{magnum}$ and passes through the vertebral canal, ending inferiorly at what vertebral level?

Between the $\text{L}1$ and $\text{L}2$ vertebrae

The deep, central groove on the front of the spinal cord that incompletely divides it into two symmetrical halves is called the:

Anterior median fissure

How many pairs of spinal nerves are given off by the spinal cord?

31 pairs

The thicker region of the spinal cord that provides innervation to the upper limbs (from $\text{C}3$ to $\text{T}1$) is the:

Cervical enlargement

The cord's tapered conical portion below the lumbar enlargement (between $\text{L}1$ and $\text{L}2$) is the:

Conus medullaris (or Medullar core)

The fibrous tissue that supports the spinal cord below the conus medullaris and anchors it to the coccyx is the:

Filum terminale

Which layer of the spinal meninges is the tough, outermost layer?

Dura mater

Which is the innermost, thin, and vascular meningeal layer that adheres tightly to the outer surface of the spinal cord, following all its contours?

Pia mater

Which region of the spinal cord gray matter contains interneurons and cell bodies for somatic and visceral **sensory** neurons?

Posterior gray horn

The cell bodies of the **alpha ($\alpha$) motor neurons**, which innervate the extrafusal muscle fibers, are located in which part of the spinal cord gray matter?

Anterior gray horn

The **lateral gray horn** is only present in the thoracic and upper lumbar regions and contains the cell bodies of what type of neurons?

Preganglionic sympathetic autonomic neurons (visceral motor)

The spinal cord's white matter is primarily organized into three regions on each side, known collectively as columns or:

Funiculi

Which type of muscle fiber is specialized and located inside a sensory organ called a muscle spindle, primarily for sensing muscle stretch and length?

Intrafusal muscle fibers

The simplest type of reflex arc, such as the stretch reflex, is characterized by having only one synapse between the sensory and motor neuron, making it a:

Monosynaptic reflex

The protective sensory receptors located in the tendon near its junction with a muscle that monitor excessive tension are called:

Tendon organs (or Golgi tendon organs)

What is the immediate outcome of the **Tendon Reflex** when excessive tension is applied to a tendon?

Sudden relaxation of the contracting muscle

What is a quick contraction of flexor muscle resulting in the withdrawal of a limb from an injurious stimulus called?

Flexor (Withdrawal) Reflex

The **crossed extension reflex** is described as a **contralateral response**. What does 'contralateral' mean in this context?

The reaction happens on the opposite side of the body from the stimulus.

The most prominent part of the Forebrain, responsible for thought, emotions, and memory, is the:

Cerebrum

The ridges or folds found on the surface of the cerebrum are called:

Gyri (gyrus)

The grooves or fissures found on the surface of the cerebrum are called:

Sulci (sulcus)

The region of the brain that surrounds the cerebrum and contains the thalamus and hypothalamus is the:

Diencephalon (interbrain)

Which part of the Diencephalon is responsible for sensory integration, acting as a major relay station for sensory information?

Thalamus

Which part of the Diencephalon is the primary head regulator for emotions, the Autonomic Nervous System (ANS), and hormone control?

Hypothalamus

Which major portion of the brain is primarily involved in fine motor control, balance, and posture?

Cerebellum

Which region of the Brainstem is primarily responsible for auditory and visual processing (containing the corpora quadrigemina)?

Midbrain

Which region of the Brainstem is involved in somatic and visceral motor control and modifies the respiratory rhythm set by the medulla?

Pons

Which region of the Brainstem contains the vital autonomic centers for controlling heart rate, breathing rhythm, and blood pressure?

Medulla oblongata

What condition is caused by inflammation of the protective membranes covering the brain and spinal cord?

Meningitis

How many interconnected cavities filled with cerebrospinal fluid (CSF) are found in the brain?

Four (two lateral ventricles, the third ventricle, and the fourth ventricle)

Cranial Nerve I (Olfactory): Function and Type:

Special Sensory: Smell (olfaction)

Cranial Nerve II (Optic): Function and Type:

Special Sensory: Vision

Cranial Nerve III (Oculomotor): Function and Type:

Motor: Controls most extraocular muscles, the eyelids, and the pupils

Cranial Nerve IV (Trochlear): Function and Type:

Motor: Innervates the superior oblique muscles

Cranial Nerve V (Trigeminal): Function and Type:

Mixed: Sensory for the face; Motor for the muscles of mastication (chewing)

Cranial Nerve VI (Abducens): Function and Type:

Motor: Innervates the lateral rectus muscles of the eye (abduction)

Cranial Nerve VII (Facial): Function and Type:

Mixed: Motor for facial expression muscles; Sensory for taste from the anterior two-thirds of the tongue

Cranial Nerve VIII (Vestibulocochlear) - Vestibular Branch Function:

Monitors balance, position, and movement

Cranial Nerve VIII (Vestibulocochlear) - Cochlear Branch Function:

Monitors hearing

Cranial Nerve IX (Glossopharyngeal): Key Sensory Function:

Receives information from the carotid sinus (BP) and carotid body ($\text{O}_2$/$\text{CO}_2$)

Cranial Nerve X (Vagus): Key Functional Division:

Part of the Craniosacral Parasympathetic Division; vital to autonomic control of visceral function

Cranial Nerve XII (Hypoglossal): Primary Function:

Provides voluntary motor control over tongue movement for speech and swallowing

The system that coordinates cardiovascular, respiratory, digestive, urinary, and reproductive functions independent of conscious will is the:

Autonomic Nervous System (ANS)

What is the structural difference in the motor pathway of the ANS compared to the Somatic Nervous System (SNS)?

The ANS uses a two-neuron chain (preganglionic and ganglionic) with a ganglion outside the CNS.

The Sympathetic Division is anatomically known as the **thoracolumbar** division because its preganglionic neurons originate in which spinal cord segments?

$\text{T}1$ through $\text{L}2$ (lateral gray horns)

What is the effect of the Sympathetic Division on the body, generally summarizing its role (the "fight or flight reaction")?

Widespread mobilization of energy and resources, increased alertness, heart rate, and metabolic rate.

What is the anatomical name for the chain of sympathetic ganglia located near the vertebral column, often leading to widespread sympathetic activation?

Sympathetic chain ganglia (or Paravertebral ganglia)

The Sympathetic Division is characterized by having preganglionic fibers that are **short** and postganglionic fibers that are **long** because ganglia are located:

Near the vertebral column

Which specialized sympathetic neurons in the adrenal glands release epinephrine and norepinephrine into the bloodstream, acting as hormones?

Chromaffin cells (in the adrenal medulla)

What is the unique neurotransmitter released by sympathetic postganglionic neurons that innervate sweat glands (a notable exception to the adrenergic rule)?

Acetylcholine ($\text{ACh}$)

The Parasympathetic Division is anatomically known as the **craniosacral** division because its preganglionic fibers originate in the brain and which spinal cord segments?

The brain (CNs III, VII, IX, X) and the sacral segments ($\text{S}2-\text{S}4$)

The Parasympathetic Division is characterized by having preganglionic fibers that are **long** and postganglionic fibers that are **short** because ganglia are located:

Near or within the target effector organ (terminal or intramural ganglia)

Which of the two ANS divisions typically has a more localized and specific effect on target organs?

Parasympathetic Division

What is the key functional role of the Parasympathetic Division?

Promoting digestion, rest, and conservation of energy (the "resting and digesting state")

The nerve network found in the walls of the digestive tract, which can function largely independently of the CNS, is called the:

Enteric Nervous System (ENS)

What neurotransmitter is released by **ALL** preganglionic neurons in both ANS divisions?

Acetylcholine ($\text{ACh}$)

What type of cholinergic receptor is always **excitatory** and found on the cell body of **all** postganglionic neurons and at somatic motor end plates?

Nicotinic receptors

What type of cholinergic receptor is found at the neuromuscular and neuroglandular junctions of both divisions, and can be either excitatory or inhibitory?

Muscarinic receptors ($\text{M}1-\text{M}5$)

What is the primary neurotransmitter released by **most** sympathetic postganglionic neurons (leading to adrenergic effects)?

Norepinephrine ($\text{NE}$)

Which adrenergic receptors primarily mediate excitatory effects like vasoconstriction, pupil dilation, and increased sweating?

Alpha-1 ($\alpha_1$) receptors

Which adrenergic receptors primarily mediate inhibitory effects like smooth muscle relaxation in the bronchioles (bronchodilation) and blood vessels in skeletal muscles?

Beta-2 ($\beta_2$) receptors

Organs that receive instructions from both the sympathetic and parasympathetic divisions are described as having:

Dual innervation

The overall level of sympathetic and parasympathetic activity that provides for continuous regulation (up or down) of organ function is known as:

Autonomic tone

The vital centers that directly control visceral functioning, such as heart rate and respiration, are primarily located in which part of the brain?

Medulla oblongata and Pons (in the brainstem)

Which brain structure acts as the 'head regulator' for the ANS, modifying brainstem activity and integrating it with emotions?

Hypothalamus

The Vagus nerve ($\text{CN X}$) is a major component of the Parasympathetic Division. Its control over the digestive tract extends to what anatomical point?

The distal half of the transverse colon