Exam 2 - BN SMU Anatomy of the NS

the brain and spinal cord

the nerves outside the brain and spinal cord, has many subdivisions
1. somatic -> controls voluntary muscles and conveys sensory information to the CNS
2. autonomic -> controls involuntary muscles
2a. sympathetic -> expends energy
2b. parasympathetic -> conserves energy

consists of the axons conveying messages from the sense organs to the CNS and from the CNS to the muscles

sensations from muscles, joints, skin, sense organs
afferent -> carry information from body's periphery to CNS

neurons that innervate (supply nerves to) skeletal muscles
efferent -> carry signals to muscles

consists of neurons that receive information from and send commands to the heart, intestines, and other organs
2 parts: sympathetic and parasympathetic nervous systems

a network of nerves that prepare the organs for a burst of vigorous activity
prepare organs for "fight or flight" -> increasing breathing and heart rate and decreasing digestive activity
for arousal, activation, and emergency

a cluster of neuron cell bodies, usually outside the CNS

consists of chains of ganglia just to the left and right of the spinal cord's central regions -> these ganglia have connections back and forth with the spinal cord
ganglia with synapses in paired columns close to the spinal cord -> form interconnected chains
Abdomen, pelvic area: synapses in ganglia close to the chains
Short preganglionic neurons, long postganglionic neurons

facilitates vegetative, non-emergency responses (digest, rest, recover from stress)
decreases heart rate, increases digestive activity, promotes sexual arousal

NOT arranged in a chain near the spinal cord!
runs largely in Vagus nerve
Ganglia with synapse close to organ or in organ walls
Long preganglionic neurons, short postganglionic neurons

because parasympathetic ganglia are not linked to one another, they act more independently than the sympathetic ganglia do

carries sensations from organs, blood gas, glucose status
Partly runs in parasympathetic nerves (in vagal nerve, large part of vagus); less differentiated than somatic sensations

neurons that innervate (supply nerves to) organs and glands
Autonomic motor neurons exit the CNS with one synapse in ganglion, then terminate on smooth muscles of the organ

release norepinephrine (noradrenaline) onto the organs
Adrenal gland: release of hormones epinephrine (adrenaline) and norepinephrine (noradrenaline) into blood
Act on α and β - adrenergic receptors
Function: integrated behavioral effects: "fight or flight"

release acetylcholine onto the organs, acts on muscarinic receptor
Function: "relax and digest", integrated behavioral effects: "conservation-withdrawal"

organs are often innervated by both systems, with antagonistic action at the organ site
opposite functions of the sympathetic and parasympathetic nervous systems, which work together to balance the ANS and maintain healthy responses to stimuli

heart rate and bronchi:
In sympathetic nervous system: heart rate is faster, bronchi relax
In parasympathetic nervous system: heart rate is slower, bronchi constrict

striate and smooth muscle

somatic nervous system, voluntary muscles
mostly around bones -> movement
Fast-acting, dependent on input from somatic motor neurons

autonomic nervous system, involuntary muscles
around hollow organs, pupil, hair follicles
Slow contraction; dependent on input from autonomic motor neurons
Also activated by stretch, hormones, or spontaneously (peristalsis; rhythmic fluctuation of resting potential)

horizontal
sagittal
coronal

a horizontal cut
shows structures as seen from above

doesn't have to be directly down the midline, can be anywhere
think cutting in perfect halfs vertically, left and right sides
shows structures as seen from the side

kind of looks like a crown
also vertical, divides into front and back sections
shows structures as seen from the front

the top of the brain is dorsal (on the same side as the animal's back) and the bottom of the brain is ventral (on the stomach side)

humans evolved to upright posture so the top of the brain is considered dorsal

towards the back

towards the stomach

towards the front end

towards the rear / back end

above another part

below another part

toward the side, away from the midline

on the same side of the body (ex: 2 parts on the left or 2 on the right)

on the opposite side of the body (ex: one on the left side and one on the right)

toward the midline, away from the side

located close to the point of origin or attachment

located more distant from the point of origin or attachment

part of the CNS, connects brain with organs and muscles below the head; segmented structure
communicates with all the sense organs and muscles except those of the head

densely packed cell bodies and dendrites of neurons that send axons to the brain or to other parts of the spinal cord through the white matter
H-shaped structure in the center of the spical cord

consists of myelinated axons of neurons; axons are organized in tracts
surrounds the gray matter

each segment has a sensory nerve and a motor nerve on both the left and right sides
each segment sends sensory information to the brain and receives motor commands from the brain

The entering dorsal roots (axon bundles) carry sensory information to the brain
The exiting ventral roots carry motor information to the muscles

in clusters of neurons outside the spinal cord on the dorsal roots, called dorsal root ganglia

inside the spinal cord

hindbrain: on bottom, connected to spinal cord
midbrain: small area under the forebrain
forebrain: very large structure that has many smaller structures inside

pons
medulla (oblongata)
cerebellum

"bridge", connects brain downwards with spinal cord, medulla, and cerebellum
Sensory pathways upwards with thalamus
contains nuclei for several cranial nerves -> left hemisphere of brain controls muscles on right side of body while right hemishphere of brain controls muscles on the left side of they body

extension of the spinal cord, controls vital reflexes, nuclei of cranial nerves that supply head and parasympathetic system (vagus nerve)

"little brain", controls movement, balance and coordination; also role in attention, perception of timing

tectum
tegmentum
substantia nigra

"roof"
includes superior colliculus and inferior colliculus -> swellings on each side of the tectum, important for sensory processing
routes for visual and auditory information

swelling on the side of the tectum, important for vision processing

swelling on the side of the tectum, important for hearing processing

underneath the tectum, "covering, carpet" -> covers several other midbrain structures, includes:
Nuclei for III. and IV. cranial nerves (eye movements)
Parts of reticular formation
Periaqueductal gray

in the midbrain, responsible for pain and defense responses

origin of dopamine pathway that facilitates readiness for movement (deteriorates in Parkinson's disease)

12 nerves that originate in the brain (hindbrain and midbrain areas)
Mostly supply the head, face, and neck region for motor control and sensation
Sensory and motor components, some cranial nerves have both, others only have one component

function for vision

control of eye movements

sensation from facial skin, 3 branches

sensations from neck and thorax, control of throat area, parasympathetic nerves to stomach, intestines, and other organs

most prominent section of the brain, consists of 2 hemispheres and multiple different subsections
each hemisphere receives sensory information from the opposite side of the body
controls muscles through axons to the spinal cord and the cranial nerve nuclei

relay station for sensory information to/from the cerebral cortex (except olfactory)
center of forebrain

controls basic vital functions → control of sexual behavior, temperature regulation, fighting, feeding, activity level, motivation
conveys messages to the pituitary glands -> alters / controls release of hormones

an endocrine (hormone-producing) gland attached to the base of the hypothalamus
synthesizes hormones that the blood carries to organs in response to messages from the hypothalamus

the outer portion of the brain, for higher cognitive function in humans
Much more sophisticated in humans than animals

large set of axons that connect the two sides (hemispheres) of the cerebral cortex

includes caudate nucleus, putamen, globus pallidus
Multiple functions and connections with cortex; involved in motor control (movement), learning, emotional expression, reward

key part of brain's system for arousal, wakefulness, and attention (intermediary between hypothalamus and cerebral cortex)

critical for formation of new memories
Important for episodic memory (specific events)
important for novelty detection
emotion: contextual information (part of limbic system)
important for spatial memory

compares current sensory input with memory

developing memory of spaces, navigating maps and 3 dimensional spaces

the "between-brain" → combination of the thalamus and hypothalamus

composite structure that extends from the top of the spinal cord through the hindbrain, midbrain, and forebrain

a set of cortical and subcortical structures that form a border around the brain stem
Often referred to as the "emotional brain"
Also has many vital functions: eating, drinking, organ perception, sexual activity)

4 fluid filled cavities within the brain connected with the central canal
each hemisphere has 2 ventricles

fluid filled channel in the center of the spinal cord

similar to blood plasma, fills the ventricles
Interconnected system, also with narrow spaces between meninges

cushion against mechanical shock; reservoir of hormones and nutrients for the brain and spinal cord
provides buoyancy, helps support the weight of the brain

thin membranes surrounding the brain and spinal cord, has pain receptors

frontal, parietal, temporal, occipital

planning of movements, recent memory, some aspects of emotions
Precentral gyrus (primary motor cortex) → fine motor movement
extends from the central sulcus to the anterior limit of the brain
contains primary motor cortex and prefrontal cortex

on precentral gyrus, controls fine movements (ex: moving a finger)

important for working memory, (delayed response tasks), planning of appropriate behavior in context, reward probability (figuring out how rewarding something is in a particular situation)
Projections from all sensory systems