UNIT 10: Nervous System Flashcards
What is the CNS composed of?
the brain and spinal cord
Where does the CNS receive input from?
from sensory neurons and it directs the activity of motor neurons that innervate muscles and glands
What nerve sends information to the brain?
sensory peripheral nerves (the brain then integrates and generates a response)
How is the brain connected to the spinal cord?
caudally. A large bundle of axonal nerve fibers that connects the spinal nerves with the brain
What do ascending tracts do?
convey sensory information from the periphery to the brain
What do descending tracts do?
they send motor nerve impulses from the brain down the spinal cord
What other abilities does the spinal cord have?
some information integration independent of the brain in the form of reflex arcs
What are the three distinct germ layers that have formed 14 days after conception?
ectoderm, endoderm and mesoderm
What happens to the ectoderm 20 days after formation?
this forms a groove that will become the neural tube
What is the neural tube?
single hollow channel that will eventually develop into the brain and the spinal cord
What are the 3 distinct swellings that come from the neural tube after 4 weeks of conception?
prosencephalon (forebrain), mesencephalon (midbrain), and rhombencephalon (hindbrain)
What happens by week 5?
the large swellings differentiate into 5 regions
What are those 5 regions?
the telencephalon and diencephalon (from the prosencephalon), the mesencephalon, and the metencephalon and myelencephalon (from the rhombencephalon)
What are ventricles?
fluid-filled chambers
What are ventricles filled with?
cerebral spinal fluid (CSF)
How is CSF produced?
by specialized tissue that lines the ventricles which is called the choroid plexuses
What does CSF do?
provides nourishment and protection as a shock absorber
What are the 4 ventricles in the human brain?
lateral (2), third and fourth ventricle
What are the lateral ventricles?
they are large paired ventricles that are found deep in the cerebral hemispheres and join the third ventricle at the level of the diencephalon
What is the third ventricle?
this is found in the diencephalon between the right and left thalamus
What is the fourth ventricle?
this is located at the level of the pons, cerebellum, and medulla
How are the ventricles joined together?
by foramen
What do the foramen do?
They facilitate the flow of CSF in and out of the brain
How are the lateral ventricles connected to the third ventricles?
vis the interventricular foramen
How is the third ventricle connected to the fourth ventricle
via mesencephalic aquaduct
How is the fourth ventricle connected to the subarachnoid space?
via the median aperture
What are the three connective tissues that encase the brain and spinal cord?
the meninges
What is the outermost layer called?
the dura mater (tough connective tissue layer)
What is the middle layer called?
the arachnoid mater (delicate membrane)
What is the inner layer called?
the pia mater (also a delicate membrane that is intimately associated with the surface of the brain)
What is the space between the pia and arachnoid mater called?
subarachnoid space (filled with CSF)
What is the purpose of the subarachnoid space?
provide a buoyant layer that protects the brain from mechanical damage
Where does CSF in the subarachnoid space drain through?
through specialized areas of the meninges called arachnoid villi and into venous circulation
Where do higher brain functions occur?
in the cerebrum (the largest part of the brain)
What is the shape of the cerebrum?
Mushroom-shaped and wrinkled structure that is found cranially and partially covers the rest of the brain
What do Sulci eventually create
elevated folds known and gyri
What are the grooves in the cerebrum called?
Sulci
What does the surface of the cerebrum look like?
it is grey matter and consists mainly of neuronal cell bodies
How can the cerebrum be divided?
into the right and left hemispheres by a deep groove called the longitudinal fissure
What is found deep in the cerebrum?
White matter mainly consists of myelinated axons that connect the grey matter with other brain areas. The few cell bodies found in white matter often collect in groups and form distinct grey areas known as nuclei
What divides the cerebrum on the coronal plane into anterior and posterior parts?
the central sulcus
What is the lateral sulcus?
a large groove that is found on each side of the brain. it delineates the temporal lobe from the frontal and parietal lobe
What is the posterior part of the cerebrum called?
occipital lobe
What is the precentral gyrus?
part of the frontal lobe adjacent to the central sulcus.
What does the precentral gyrus consist of?
consists of upper motor neurons which send axons down through the brain and spinal cord to synapse lower motor neuron
What is the precentral gyrus also involved in?
involuntary muscle movement (lower motor neurons leave the spinal cord as the PNS and innervate skeletal muscle at neuromuscular junctions)
What is the area adjacent to the central sulcus on the parietal lobe called?
postcentral gyrus
What is the postcentral gyrus involved in?
Somatic sensation from receptors all over the body
What does the temporal lobe contain?
neurons important for the interpretation of senses, and the occipital lobe is important for visual stimuli
What are the basal nuclei and limbic system?
nuclei that lie deep to the surface of the cerebrum that are important for higher brain function in humans
What are the cerebral lobes?
Frontal, parietal, temporal, occipital, and insula
What is the frontal lobe function?
voluntary motor control of skeletal muscles, personality, higher intellectual processes, and verbal communication
What is the parietal lobe function?
cutaneous and muscular sensations, speech, textures, and shapes
What is the temporal lobe function?
auditory sensation, memory of auditory and visual experiences
What is the occipital lobe function?
Integration of movements in focusing eyes, correlation of visual images with images
What is the insula lobe function?
memory, pain, and visceral integration
What is the basal nuclei?
various collections of cell bodies found in the white mater of the cerebrum and they are critical for proper body movements
What are upper motor neurons?
they are of the motor cortex and they send axons deep into the cerebrum where they then synapse on the basal nuclei
What happens once received?
the impulses are transferred to different areas of the basal nuclei in complex circuits and are eventually relayed to the thalamus or the cerebellum
What do the thalamus and the cerebellum do?
send the majority of the signals back to the motor cortex thus forming an accessory motor system
Why is the accessory motor system important?
it determines how rapid a movement will occur and how large that movement will be
What does the limbic system consist of?
this consists of various brain regions that are responsible for emotion, behavior, motivation, long-term memory, and smell
What areas of the cerebrum does the limbic system consist of?
cingulate gyrus, amygdala, hippocampus, septal nuclei, the anterior insula, and the hypothalamus and thalamus
What else is the limbic system also critical for?
emotional drives and forms complex connections with the thalamus and hypothalamus
Are the limbic system and the cerebral cortex connected?
No
What emotions are associated with the limbic system?
aggression, fear, feeding patterns, sex drive, and reward and punishment systems
What does the diencephalon consist of?
thalamus and hypothalamus
What pathways are included in the connection between the thalamus and cerebral cortex?
motor and sensory pathways
What does relaying on sensory information from the thalamus do?
provides and interpretation of sensation based on previous experience. ( good vs bad, hot vs cold [crude sensation])
What is a small structure in the diencephalon?
the hypothalamus
What does the hypothalamus control?
lower autonomic functions, or bodily functions that occur involuntarily (heart rate). This includes the autonomic, nervous, and endocrine system as the hypothalamus extends axonal projections into the posterior pituitary
Hypothalamus= ???
body’s thermostat and preforms homeostasis
What does the hypothalamus do to increase body temperature?
induces vasoconstriction in surface blood vessels that will decrease blood flow to the surface of the body and thus the blood loss inhibits eccrine sweat glands.
What do eccrine sweat glands do?
Prevents sweating and further heat loss. It can also induce shivering to increase heat protection by muscular contractions
What does the hypothalamus do to decrease body temperature?
it vasodilates the surface blood vessels and induces sweating
What else does the hypothalamus do?
contains hunger and thirst centers and also contributes to emotion and behaviour
What is the mesencephalon?
the midbrain. it forms the upper part of the brainstem, which connects the pons and cerebellum with the diencephalon.
What does the mesencephalon include?
corpora quadrigemina, cerebral peduncles, red nucleus, substantia nigira
What is corpora quadrigemina?
visual and auditory reflexes
What are the cerebral peduncles?
ascending and descending tracts
What is the red nucleus?
connects the cerebrum to the cerebellum and is involved in motor coordination
What is the substantia nigira?
an important part of the motor circuit
What is the rhombencephalon?
the hindbrain. it is composed of the metencephalon superiorly and myelencephalon inferiorly
What is the metencephalon comprised of?
pons and the cerebellum
What is the myelencephalon comprised of?
medulla oblongata
Where are the two respiratory control centers found?
Apneustic and pneumotaxic
What do the pons do?
connects, or bridges any descending pathways from the cerebral cortex to the cerebellar cortex and medulla, and ascending pathways travelling through the medulla to the thalamus crainally
What do the pons and medulla do together?
the regulate respiration depth and frequency
How are the pons connected to the cerebellum?
surface fibers
What is the myelencephalon?
consists of the medulla oblongata, which is a conduit for ascending and descending nerve fiber tracts that connect the spinal cord to the rest of the brain
Why are the vital centers important in the medulla?
autonomic control of the heart and peripheral blood vessels, respiratory rate and depth and sneezing
What is reticular formation?
connects various areas of the brain and processes a great deal of neuronal information.
What does the ascending tract of the reticular formation determine?
consciousness. it is also termed the reticular activity system (RAS)
What is the spinal cord?
continuation of the medulla caudally as it leaves the skull through a large opening termed the magnum foramen.
What is the spinal cord protected by?
protected from damage by the bony vertebral column, the meninges, and CSF
Where do afferent nerves enter the spinal cord?
they branch from the spinal cord into the dorsal root
Where do efferent nerves leave the spinal cord?
they leave by the ventral root
What happens when ventral and dorsal roots combine before leaving the vertebral column?
forms a peripheral spinal nerve
Order from the outermost to the innermost
dura, arachnoid, and pia maters
What else can the CSF provide?
nutrition and shock-absorbing protection
What do ascending tracts convey?
sensory information from the body to the brain
What do descending tracts convey?
they transmit efferent information from the brain to the target tissues
What are the major ascending tracts to know?
spinocerebellar tract and the spinothalamic tracts
What does the spinocerebellar tract do?
convey sensory, and proprioceptive information to the cerebellum
What does the spinothalamic tracts do?
convey pain and temperature to the thalamus
What are the major descending tracts to know?
corticospinal tract, and extrapyramidal tracts
What is a reflex?
involuntary response to a stimulus (the spinal cord provides integrated functions independent of the brain to form reflex arcs)
What is a monosynaptic reflex?
a reflex arc that has a minimum: a sensory receptor to detect a stimulus, a sensory neuron to transmit to the spinal cord, and a motor neuron
What reflex is essential for maintaining proper posture?
the knee jerk reflex (patellar tendon below the knee)
What type of reflex is the knee reflex?
ipsilateral reflex (same side reflex)
What is a flexor reflex?
when there is a painful stimuli in the limbs (grabbing hot pan)
What is a cross-extensor reflex arc?
crosses the midline of the body to mediate contraction of extensor muscles on the opposite limb to support the body’s weight (when something is pricked instead of hot)
What type of reflex is a cross-extensor reflex arc?
polysynaptic, contralateral reflex arc
What is the peripheral nervous system (PNS)?
consists of nerves that connect to the CNS and all sensory receptors and effectors in the body. (axons grouped and bundled into nerves)
Olfactory
sense of smell (sensory)
Optic
vision (sensory)
Oculomotor
eye movements
Trochlear
eye movements (motor)
Trigeminal
somatic sensation from the face, mouth, cornea, and chewing (both)
Abducens
eye movements (motor)
Facial
muscles for facial expression (both)
Vestibulocochlear
hearing and sense of balance (sensory)
Glossopharyngeal
sensation from the pharynx, taste sensation from the posterior of the tongue, carotid baroreceptors (both)
Vagus
autonomic functions of the gut and thorax, sensation of the pharynx, muscle and vocal cords, swallowing reflex (both)
Spinal Accessory
somatic innervation of the shoulder and neck muscles (motor)
Hypoglossal
somatic innervation of the tongue (motor)
Where do spinal nerves arise from?
directly from the spinal cord
How many pairs of spinal nerves do humans have?
13
What is a plexus?
combination or network of nerves that supply a specific region of the body
What are autonomic motor nerves?
innervate organs whose functions are NOT usually under voluntary control
What effectors respond to autonomic motor nerves?
heart, smooth muscle, and glands
What are the two major categories of motor neurons?
somatic and autonomic
What are somatic motor neurons?
have their cell bodies within the CNS and send axons to skeletal muscles, which are usually under voluntary control
What are autonomic motor neurons?
they involve two neurons in the efferent neurons.
What are preganglionic autonomic fibers?
originate in the midbrain and hindbrain
Where are autonomic ganglia located?
in the head, neck, abdomen
What are the two divisions of the autonomic nervous system?
sympathetic and parasynpathetic
Which ones consist of preganglionic neurons?
both
What is the sympathetic division called?
thoracolumbar division.
What is para-vertebral ganglia?
somatic motor fibers with postganglionic neurons within a double row of sympathetic ganglia
What is it called when the ganglia rows are interconnected?
they form a sympathetic chain of ganglia
Where are sympathetic axons distributed?
skeletal muscles and the skin in the body
What do preganglionic fibers form?
splanchnic nerves
What organs do the postganglionic fibers that arise from the collateral ganglia innervate?
digestive, urinary, and reproductive systems
Where are adrenal glands located?
above each kidney
How many parts is the adrenal gland composed of?
2: an outer cortex and inner medulla
What does the adrenal cortex do?
secretes steriod hormones
What does adrenal medulla do?
secretes epinephrine (adrenaline) and to a lesser degree norepinephrine
What is the parasympathetic division?
known as the craniosacral divison
Where do the preganglionic parasympathetic fibers synapse?
in the ganglia
What is the major difference between the sympathetic and parasympathetic divisions?
the sympathetic division, the ganglion cells are typically outside the target organs
What is found in both systems?
cholinergic (producing acetyl choline) but the postganglionic fibers are different
Which system is the “fight or flight”
sympathetic
What prepares the body for intense physical activity in emergencies?
sympathetic
What regulates heart, blood vessels and other organs
sympathetic
What antagonized the sympathetic division?
parasympathetic
What allows the body to “rest and digest” through the release of ACh
parasympathetic
What slows heart rate and increases digestive activities?
parasympathetic
What does adrenergic stimulation have?
both excitory and inhibitory effects
What are the two major classes of receptor proteins?
alpha and beta-adrenergic receptors (each have subtypes)
What does the stimulation of a1 adrenergic receptors cause?
contraction of smooth muscles
Is acetyl choline a neurotransmitter?
Yes
What happens to the stimulation of beta-adrenergic receptors do?
promotes the relaxation of smooth muscles but increases the force of contraction of cardiac muscle and promotes an increase in heart rate
What effect does ACh released by somatic motor neurons have?
they are always excitatory (can be inhibitory in parasympathetic division)
What are the two main types of cholinergic receptors?
nicotinic and muscarinic
Where are they located?
neuromuscular junction of skeletal muscle fibers and in the autonomic ganglia
What stimulates the ACh muscarinic receptors in the visceral organs?
muscarine and ACh
What type of channels are the nicotinic ACh receptors?
ligand- gated ion channels
Why are nicotinic ACh receptors always excitory?
they are depolarized
What are muscarnic ACh receptors?
coupled to G-proteins, which can either close or open different membrane channels and activate different membrane enzymes (excitatory or inhibitory)
