PY715 Quiz 3: The Nervous System, Hindbrain, and Midbrain

Neurons

Another name for nerve cells

Reflex

Rapid, predictable, and involuntary response to a stimulus

Sensory neurons (afferent)

Neurons that carry incoming information from the sensory receptors to the brain and spinal cord

Motor neurons (efferent)

Neurons that carry outgoing information from the brain and spinal cord to the muscles and glands

Mixed neurons

Contain both sensory and motor neurons

Where are sensory receptors located?

At the ends of peripheral neurons throughout internal organs and the skin

Medial

toward the middle

Lateral

toward the side

Proximal

near to

Distal

far from

Ipsilateral

on the same side

Contralateral

on the far side

Bilateral

on both sides

Left & Right

from the owner's perspective

Nerve

a bundle of axons

What is an analogy for a nerve?

a bundle of electrical wire that makes up a larger cable

Nucleus/Nuclei

group of cell bodies inside CNS

Ganglion/Ganglia

group of cell bodies outside CNS

Commissure

lateral pathway (connect left to right)

Corpus callosum

the most important/largest commissure in the brain

White matter (axons)

pathways are always this type of matter

What are the two main components of the central nervous system?

The brain and spinal cord

What encloses the central nervous system?

Bone (cranium and spinal column)

What protective covering wraps the central nervous system?

Meninges (Dura Mater -> Arachnoid -> Pia Mater)

What fluid bathes the central nervous system?

Cerebrospinal fluid (CSF)

What are the main components of the peripheral nervous system?

everything in the nervous system that isn't the brain and spinal cord

What two nerves make up the peripheral nervous system?

cranial nerves and spinal nerves

What two neurons does the peripheral nervous system communicate through?

afferent (sensory) neurons and efferent (motor) neurons

In what direction do the PNS neurons communicate?

into and out of the CNS

PNS

everything else

Cranial Nerves

Connect to the brain

How many pairs of cranial nerves are there?

12 pairs

What type of neurons are cranial nerves?

motor (efferent), sensory (afferent) or mixed

Spinal Nerves

Connect to the spinal cord (have ganglia)

How many pairs of spinal nerves are there?

31 pairs

What type of neurons are spinal nerves?

all mixed nerves

The dorsal (sensory) root of a spinal nerve carries _______ information from the _______ to the _______.

sensory information from the skin/body to the spinal cord

The ventral (motor) root of a spinal nerve carries _______ information from the _______ to the _______.

motor information from the spinal cord to the muscles.

The ______ spinal and cranial nerves mediate _______ processes

the same spinal and cranial nerves mediate different processes within both the somatic and autonomic nervous systems

Somatic Nervous System

innervates striated muscles (purposeful/voluntary movement)

What structure initiates the somatic nervous system?

frontal lobe, meaning this is a conscious choice

Autonomic Nervous System

innervates smooth muscles of internal organs (glands, blood vessels)

What structure initiates the autonomic nervous system?

hypothalamus (involuntary reactions)

How does the hypothalamus initiate the autonomic nervous system?

the hypothalamus initiates the secretion of hormones into the bloodstream that innervate smooth muscles of internal organs

What are the two subdivisions of the autonomic nervous system?

Sympathetic (fight or flight) and Parasympathetic (rest or digest) nervous systems

The autonomic nervous system is _______ beyond conscious control and _______ be influenced by conscious decisions

the autonomic nervous system is not beyond conscious control and can be influenced by conscious decisions

Sympathetic Nervous System

fight or flight

Parasympathetic Nervous System

rest or digest

Are there functional and anatomical differences between the sympathetic and parasympathetic nervous system?

Yes, there are both functional and anatomical differences

What are the functional differences of the sympathetic vs. parasympathetic nervous system?

the sympathetic system triggers the "fight or flight" response to prepare the body for action, while the parasympathetic system controls the "rest and digest" state for recovery and normal body functions

What are the anatomical differences between the sympathetic vs. parasympathetic nervous system?

Sympathetic Nervous System:

- thoracolumbar source (thorasic (middle) + lumbar nerves)

- ganglia located close to the spinal cord

- short neuron (from spinal cord to the ganglion)

- uses both acetylcholine and norepinephrine

Parasympathetic Nervous System:

- craniosacral source (cranial (top) + sacral (bottom) nerves)

- ganglia located closer to the muscle

- long neuron (from ganglion to the effector/muscle)

- uses only acetylcholine

What is the origin of the sympathetic nervous system?

Thoracolumbar source; para- and prevertebral ganglia.

What is the origin of the parasympathetic nervous system?

Craniosacral source; ganglia near the effector/muscle.

What are three major divisions of the brain?

Forebrain, Midbrain, Hindbrain.

Axons are

White matter (roads)

Dendrites and soma are

Grey matter

The primary function of white matter is

Communication

The primary function of grey matter is

Processing

Describe the matter composition of the CNS

The grey matter (hemispheres) are suspended in white matter

What are the two main components of the hindbrain?

The medulla and pons.

What reflexes are controlled by the hindbrain?

Life-sustaining reflexes such as cardiac (heart rate), circulatory (blood pressure), and respiratory reflexes.

What is the significance of decussation in the nervous system?

It refers to the crossing over of nerve fibers, leading to contralateral control.

What is the significance of contralateral control in the nervous system?

It refers to functions and information from one side of the brain being processed and controlled by the opposite side.

In order for higher parts of the brain to send out information as well as receive information from the rest of the body, the information must pass through the _______.

Hindbrain (remember this is the lowest structure of the brain, closest to the brainstem)

What direction(s) are the pathways in the Medulla and Pons?

Ascending and descending pathways, because information must come into and out of the brain

The pathways of the medulla and pons are affected by what two organizational components?

Decussation (physical crossing of neural pathways) and contralateral control (resulting function in which one side of the brain controls the opposite side of the body)

What is the role of the reticular formation?

To determine the level of arousal and consciousness by controlling the level of activity in neurons

Where does reticular formation communication project?

Projected to most of the cortex, neurons are connected everywhere, which is important for consciousness/alertness

What are the four levels of arousal as determined by the reticular formation?

Alert, drowsy, stuporous, comatose

Damage to the reticular formation causes

Loss of consciousness or coma

What does the cerebellum control?

Coordination, posture, and balance.

The cerebellum is largely _______ based but plays an important role in _______ such as coordination of speech.

The cerebellum is largely motor based but plays an important role in cognition such as coordination of speech.

Tandem gait test

a coordination task where the toes of the back foot touch the heel of the front foot at each step to assess cognitive state (i.e., drunkenness)

What structures are found in the midbrain?

Tectum and Tegmentum

Tectum

the dorsal part of the midbrain; includes the superior and inferior colliculi, "roof" of the midbrain

What is the function of the superior colliculi?

Visual reflexes.

Cortical blindness (blindsight)

Inability to perceive visual information/light but a retained reflex to visual information

What is the function of the inferior colliculi?

Auditory reflexes and sound localization.

What two components are used in sound localization?

Speed (how fast it reaches the left vs. right ear) and Volume (how loud it is when it reaches the left vs. right ear)

Tegmentum

The ventral part of the midbrain; includes the autonomic (automatic) eye motor nuclei and substantia nigra, "floor" of the midbrain

What two muscles make up the autonomic eye motor nuclei in the tegmentum?

Ciliary muscle (lens) and sphincter muscle (iris)

Ciliary muscle

Controls the contraction or relaxation of the lens to assist in near or far vision respectively

Sphincter muscle of iris

Controls the amount of light passing through the iris by contracting or dilating

What does the substantia nigra control?

Motor control.

What disorder is implicated in damage to the substantia nigra?

Parkinson's Disease

What is the reticular formation?

A set of interconnected nuclei that are located throughout the midbrain (tegmentum) and the hindbrain (pons and medulla).

Describe the reticular formation pathway

Information travels from the reticular formation through the thalamus and out into various areas of the brain