Chapter 13: Brain and Cranial Nerves Flashcards
What are the four main divisions of the brain?
- Brainstem
- Cerebellum
- Diencephalon
- Cerebrum
What is the Function of the Brainstem?
- connects spinal cord to cerebrum
- includes medulla oblongata, pons, midbrain, and reticular formation
Function of the Medulla Oblongata
- path for ascending/descending nerve tracts
- center for reflexes (vomiting, heart rate, breathing, swallowing)
Function of Pons
- has ascending and descending nerve tracts
- send info btwn cerebrum and cerebellum
- center for reflexes
What are the parts of the brainstem?
- Medulla Oblongata
- Pons
- Midbrain
What are the parts of the Diencephalon?
- Thalamus
- Hypothalamus
- Epithalamus
- Subthalamus
What is the function of the superior colliculi?
- receive visual, auditory, and touch sensory info
- part in eyes, head, & body reflexes
What is the function of the inferior colliculi?
- necessary for hearing
- important in auditory pathways of CNS
What is the function of tegmentum?
- ascending tracts
- carry sensory info from spinal cord to brain
What is the function of the cerebral peduncles?
- descending tracts
- carry motor info from cerebrum to brainstem and spinal cord
What are the parts of the midbrain?
- superior colliculi
- inferior colliculi
- cerebral peduncles
- tegmentum
What is the function of the reticular formation?
- cluster of nuclei
- aid in awareness and arousal
What is the function of the cerebellum?
- control posture & fine motor movements
- have 3 peduncles connecting cerebellum to pons, midbrain, & medulla oblongata
- communicates with CNS through peduncles (tracts)
What is the function of the thalamus?
- sensory relay center of brain
- some effect w emotions (fear & rage)
- connect to prefrontal cortex and limbic system
Function of subthalamus
help control motor functions
Function of epithalamus
- behavior
- “sleep-wake” cycle (pineal gland)
Function of hypothalamus
- smell/reactions related to smell
- controls endocrine system
- digestion/heart rate
- body temp
Function of cerebrum
- largest part of brain
- left & right hemispheres
- contains primary motor cortex & primary somatosensory cortex
- divided into lobes
- gray matter = cerebral cortex
- white matter = cerebral medulla
What are the three types of fibers in the cerebral medulla?
- commissural
- association
- projection
What are commissural fibers?
fiber that connect one hemisphere of the brain to the other hemisphere
What are association fibers?
fibers that connect areas of cerebral cortex to same hemisphere
What are projection fibers?
fibers that connect the cerebrum to other parts of the brain/spinal cord
Function of limbic system
- part of cerebrum and diencephalon
- emotion, learning, memory, motivation
Central Nervous System (CNS)
- Brain
- Spinal cord
- Function: receives info from PNS & interprets/makes decisions
Peripheral Nervous System (PNS)
- nerves
- ganglia
- Function: collects info inside & outside of body & sends to CNS/carries out decisions of CNS
What are the 4 segments of the spinal cord?
- Cervical
- Thoracic
- Lumbar
- Saccral
How many pairs of spinal nerves are in the spinal cord?
31 pairs
What are the 2 enlargements of the spinal cord?
- Cervical enlargement -> upper limb nerves
- lumbosaccral enlargement -> lower limb nerves
What are spinal meninges?
connective tissue around spinal cord and brain separating them from bones
- protect spinal cord and brain
- passageway for blood vessels of brain/spinal cord
How many meningeal layers are there?
3 layers
What are the 3 meningeal layers from superficial to deepest?
- Dura Mater
- Arachnoid Mater
- Pia Mater
What are the 3 spaces in between the spinal cord meninges?
- epidural space (btwn bone and dura mater)
- subdural space (btwn dura mater and arachnoid mater)
- subarachnoid space (btwn arachnoid mater and pia mater)
What is the clinical significance of epidural space?
- separates vertebral canal and dura mater
- spinal roots, blood vessels, areolar connective tissue, adipose tissue
- around brain - potential space
- epidural anesthesia -> inject anesthetics into epidural space of spinal cord
What is the clinical significance of subarachnoid space?
- separates arachnoid mater from dura mater
- blood vessels, cerebrospinal fluid (CSF), strands of arachnoid mater
How is the spinal cord secured in the spinal column?
- held ini thecal sac by denticulate ligaments & filium terminale
- denticulate ligaments: connective tissue from outside sides of spinal cord to dura mater (prevent spinal cord from moving side to side)
- filium terminale: strand of connective tissue (stops spinal cord from moving up and down)
Function of anterior median fissure and posterior median sulcus
separates 2 halves of spinal cord
White Matter
- myelinated axons
- nerve tracts
- 3 columns (ventral, dorsal, & lateral)
- columns divided into tracts (ascending & descending)
Gray Matter
- neuron cell bodies
- dendrites
- axons
- horns (dorsal, ventral, lateral horns)
- commissures (gray & white commissures)
Function of spinal nerves
- sensory and motor info
Dorsal Root
- afferent
- sensory info
Ventral Root
- efferent
- motor (muscles/glands)
Dorsal Root Ganglion
- group of sensory neuron cell bodies
- axons synapse with interneurons in dorsal horn
Ventral Root
- somatic motor neurons (ventral horn)
- autonomic motor neurons (lateral horn)
What are the different kinds of spinal nerves and # of pairs?
- Cervical (8 pairs)
- Thoracic (12 pairs)
- Lumbar (5 pairs)
- Sacral (5 pairs)
- Coccygeal (1 pair)
Endoneurium Layer
- layer of connective tissue surrounding each axon
Perineurium Layer
- thicker layer of connective tissue surrounding groups of axons (fascicles)
Epineurium Layer
3rd layer connective tissue binding fascicles tg to form a nerve
What are dermatomes?
regions of the skin controlled by a pair of neurons
What is the clinical significance of dermatomes?
Shingles - reactivated virus in dorsal root ganglion or ventral root, travels through sensory axons along dermatome in form of rash/blisters on surface of skin
What are nerve plexuses?
braids of spinal nerves
How many nerve plexuses are there?
5 plexuses
What are the 5 nerve plexuses?
- cervical plexus (C1-C4)
- brachial plexus (C5-T1)
- lumbosacral plexus (L1-S4)
- coccygeal plexus (S5-C0)
Cervical Plexus
- (C1-C4)
- innervate neck muscles, skin, & back of head
- phrenic nerve (breathing)
Brachial Plexus
- (C5-T1)
5 ventral rami (main nerve branches) - join into 3 trunks
- split into 6 divisions
- join to form 6 cords
- form 5 branches
Lumbosacral Plexus
-(L1-S4)
4 major nerves
- obturator
- femoral
- tibial
- fibular
What is a reflex
automatic response to a stimulus
What are the steps to a reflex arc?
- sensory receptor detects stimulus
- sensory neuron creates AP through nerve & dorsal root to spinal cord
- integration center - AP brought to integration center
- motor neuron - interneuron synapses w motor neuron
- effector organ - motor neuron axon brings motor neuron through ventral root to effector organ
What are the 4 main types of reflexes?
- developmental
- complexity
- effector
- integration center
What are the kinds of developmental reflexes?
- innate: part of normal develop.
- learned: developed after repetition of activity
What are the kinds of complexity reflexes?
- monosynaptic: sensory neuron synapses on ONE motor neuron @ integration center
- polysynaptic: one interneuron between sensory & motor neuron
What are the kinds of effector reflexes?
- somatic: skeletal muscle
- autonomic: cardiac muscle, smooth muscle, or glands
What are the kinds of integration center reflexes?
- spinal: in spinal cord
- cranial: in brain
What is a contralateral reflex arc?
impulse from receptor on opposite side of spinal cord
- ex. step on object w foot (right leg contracts to keep balance while moving left leg away)
What is an ipsilateral reflex arc?
receptor & effector organ are on the same side of the spinal cord
- ex. remove hand from hot stimulus
What is the patellar reflex?
- patellar tendon is tapped w a hammer
- receptors (muscle spindles) in quadriceps femoris stretch
- AP’s go up sensory neuron to spinal cord
- sensory neuron synapses onto motor neuron
- AP releases acetylcholine (ACH) to effector (quadriceps femoris) to contract again so does not overstretch
- monosynaptic & ipsilateral
What is the flexor reflex (withdrawal reflex)?
- sensory neuron carries AP to interneuron on dorsal gray horn
- interneuron sends info to brain, agonist, and extensors
- polysynaptic & intersegmental
What is the crossed extensor reflex?
- works alongside flexor reflex
- step on something sharp. Body lifts leg and shifts weight onto the other
- sensory neuron send AP through dorsal root ganglion to synapse on dorsal gray horn
- interneurons carry AP to motor neurons to lift leg
- axons of interneuron travel to other side (cross) to synapse on ventral gray horn
- stimulates extensors to stay straight & allow body to shift weight
- contralateral, polysynaptic, intersegmental
What is reciprocal inhibition?
when a sensory neuron detects a stimulus and travels to the integration center
Why is reciprocal inhibition important?
- sensory neuron splits into 3 (brain, dorsal gray horn, & ventral gray horn)
- dorsal gray horn neuron connects to motor neuron & not enough AP is generated to excite antagonistic muscle (relaxes)
- ventral gray horn AP travels to muscle & excites causing it to lift
- polysynaptic & ipsilateral
How can the brain affect spinal cord reflexes?
through facilitation and/or inhibition
What is facilitation in spinal cord reflexes?
neurons in a pathway/tract that are partially depolarized
- small amount of AP
What is inhibition in spinal cord reflexes?
send ISPS through efferents ascending pathways
What is the Babinski reflex?
- normal in infants
- inhibition
- in adults by maturation of descending motor tracts
- toes curl up
What are the steps of flow of cerebrospinal fluid (CSF)?
- created in choroid plexus by ependymal cells
- secreted from choroid plexus in lateral ventricles
- flows into 3rd ventricle
- flows through cerebral aqueduct into 4th ventricle
- then flows into subarachnoid space to central canal of spinal cord
- flows around brain to dura venous sinuses
- drains into dural venous sinuses (jugular veins)
- extra CSF turns into blood
- protects brain
What are functional areas of the cerebral cortex?
- primary motor cortex, premotor cortex, Broca’s area
- central sulcus
- primary somatosensory cortex, somatosensory association cortex
- Wernicke’s area
