neurophysiology (nervous system)

Question 1

peripheral nervous system VS central nervous system:

Answer 1

The CNS includes the brain and spinal cord (= brain + spinal cord), while the peripheral nervous system consists of everything else. (cranial nerves, spinal nerves and their roots and branches, peripheral nerves, and neuromuscular junctions = nerves and sensory organs)

Question 2

somatic VS autonomic nervous system:

Answer 2

he somatic nervous system is responsible for voluntary actions such as scratching an itch. The autonomic nervous system is responsible for most involuntary movements in the body such as digestion

Question 3

PNS = divided into 3 parts:

Answer 3

SNS : voluntary (skeletal muscles)
ANS: involuntary (smooth muscles)
ENS: “brain” of the gut = GI tract NS
all communicate with CNS

Question 4

rubrospinal tract:

Answer 4

riginates in the red nucleus and
projects to motoneurons in the lateral spinal cord.
Stimulation of the red nucleus produces activation of flexor
muscles and inhibition of extensor muscles

Question 5

pontine reticulospinal tract:

Answer 5

originates in nuclei of the
pons and projects to the ventromedial spinal cord.
Stimulation has a generalized activating effect on both flexor
and extensor muscles.

Question 6

medullary reticulospinal tract:

Answer 6

originates in the medullary
reticular formation and projects to motoneurons in the spinal
cord. Stimulation has a generalized inhibitory effect on both
flexor and extensor muscles.

Question 7

lateral vestibulospinal tract

Answer 7

riginates in the lateral
vestibular nucleus (Deiters’ nucleus) and projects to
ipsilateral motoneurons in the spinal cord. Stimulation
produces activation of extensors and inhibition of flexors.

Question 8

tectospinal tract

Answer 8

originates in the superior colliculus and
projects to the cervical spinal cord. It is involved in control of
neck muscles.

Question 9

pyramidal tracts:

Answer 9

are corticospinal and
corticobulbar tracts
that pass through
the medullary
pyramids and
descend directly
onto lower
motoneurons in the
spinal cord

Question 10

The ventricular system of the human brain:

Answer 10

• The cerebral ventricles are a series
  of interconnected, fluid (CSF) filled
  spaces that lie in the core of the
  forebrain and brainstem
• produced by a modified vascular
  structure called the choroid plexus

Question 11

functions of the CSF:

Answer 11

Protection: the CSF protects the brain from damage by “buffering” the brain. In other words, the CSF acts to cushion a blow to the head and lessen the impact.
Buoyancy: because the brain is immersed in fluid, the net weight of the brain is reduced from about 1,400 g to about 50 g. Therefore, pressure at the base of the brain is reduced.
Excretion of waste products: the one-way flow from the CSF to the blood takes potentially harmful metabolites, drugs and other substances away from the brain.
Endocrine medium for the brain: the CSF serves to transport hormones to other areas of the brain. Hormones released into the CSF can be carried to remote sites of the brain where they may act.

Question 12

circulation of the CSF (AV drainage)

Answer 12

slide 28

Question 13

preganglionic VS postganglionic functions:

Answer 13

These neurons are known as preganglionic neurons and travel to ganglia, where they synapse and activate nicotinic receptors on postganglionic neurons using acetylcholine. The postganglionic neurons then travel to the target site and release norepinephrine to activate adrenergic receptors.

Question 14

neurotransmitters in the autonomic nervous system:

Answer 14

Acetylcholine (ACh)
– used in both the parasympathetic and sympathetic
nervous system (cholinergic nerves)
Norepinephrine (NE) (also referred to as noradrenaline)
– in the periphery used only in the sympathetic nervous
system (adrenergic nerves)
Epinephrine (EPI) (also referred to as adrenaline)
– a hormone released from the adrenal medulla
Acetylcholine is the neurotransmitter at all autonomic ganglia

Question 15

sympathetic VS para pre + postganglionic neurons:

Answer 15

• Most sympathetic post-ganglionic neurons release norepinephrine to act on adrenergic receptors of target organs. However, there are some exceptions, such as the sweat glands, where acetylcholine is released by post-ganglionic neurons and binds to muscarinic receptors.
  (Acetylcholine is released from pre-ganglionic neurons and binds to nicotinic receptors on post-ganglionic neurons.)
• the parasympathetic: Pre-ganglionic neurons: Acetylcholine is released from pre-ganglionic neurons and binds to nicotinic receptors on post-ganglionic neurons (similar to the sympathetic system).
  Post-ganglionic neurons: Acetylcholine is also released by parasympathetic post-ganglionic neurons, but it acts on muscarinic receptors located on the target organs.

Question 16

tissue responses define receptors:

Answer 16

Smooth Muscle Responds to ACh and Muscarine
(Muscarinic Cholinergic Receptor)
Skeletal Muscle Responds to ACh and Nicotine
(Nicotinic Cholinergic Receptor)
!! Acetylcholine is the neurotransmitter at all autonomic ganglia !!

Question 17

muscarinic vs nicotinic receptors (both for AcH)

Answer 17

• Nicotinic receptors function within the central nervous system and at the neuromuscular junction. While muscarinic receptors function in both the peripheral and central nervous systems, mediating innervation to visceral organs
• Nicotinic cholinergic receptors stimulate sympathetic postganglionic neurons, adrenal chromaffin cells, and parasympathetic postganglionic neurons to release their chemicals. Muscarinic receptors are associated mainly with parasympathetic functions and are located in peripheral tissues (e.g., glands and smooth muscle).
  you also find adrenergic in (only) sympathetic

Question 18

Norepinephrine is the neurotransmitter:

Answer 18

at most sympathetic nerve terminals
There are three exceptions

Question 19

Exceptions in the sympathetic nervous system:

Answer 19

• Sweat glands: Postganglionic sympathetic neurons involved with sweating release acetylcholine. They are called sympathetic cholinergic
  neurons
• Kidneys: Postganglionic neurons to the smooth muscle of the renal
  vascular bed release dopamine
  Exceptions in the Sympathetic Nervous system II and III
• Adrenal gland: Preganglionic neurons do not synapse in the paravertebral
  sympathetic ganglion
  » Preganglionic neurons
  synapse directly on the
  adrenal gland, release
  acetylcholine, and activate
  nicotinic receptors on the
  adrenal gland
  » Adrenal glands release
  epinephrine and
  norepinephrine (4:1) into the
  systemic circulation

Question 20

Ascending VS descending tracts (neurons of spinal cord from neural tracts)

Answer 20

• Ascending: carry sensory input to the brain
• Descending: send motor commands downwards to the body

Question 21

Local circuit neurons in the
spinal cord gray matte

Answer 21

• Pathways that contact the medial parts of the spinal cord gray matter are Involved (terminate bilaterally)
  primarily In the control of posture
• Those that contact the lateral parts are involved in the fine control of the distal extremities. (always terminating on the same side of the cord as the cell body)

Question 22

Reflex arc:

Answer 22

spinal reflexes involve circuits of sensory nerve fibers that feed information to the spinal cord and then connect directly, or via an intermediate neuron, to motor nerve fibers, so that the resulting instructions for movements go directly out from the cord to the relevant muscles and not to the brain, to be activated

Question 23

what is a dermatome ?

Answer 23

dermatome is an area of the skin in which all
cutaneous fibers track back to the same spinal level
(i.e., they all go into the spinal cord at, say, at C8, which
would define C8 dermatome)
- Cutaneous fibers that all map to the same spinal level =
dermatome but the fibers of the same dermatome may
reach the spinal cord via different cutaneous nerves

Question 24

skin mechanoreceptors:

Answer 24

• Merkel cell afferents are slowly adapting fibers that account for about 25% of the mechanosensory afferents in the hand. They are especially eriched in the fingertips, and are the only afferents to sample information
  from receptor cells located in the epidermis.
• Meissner afferents are rapidly adapting fibers that innervate the skin even more densely than Merkel afferents, accounting for about 40% of the mechanosensory innervation of the human hand.
• Pacinian afferents are rapidly adapting fibers that make up 10-15% of the mechanosensory innervation in the hand. Pacinian corpuscles
  are located deep in the dermis or in the
  subcutaneous tissue;
• Ruffini afferents are slowly adapting fibers and are the least understood of the cutaneous mechanoreceptors.
• Ruffini endings are elongated, spindle-shaped, capsular specializations located deep in the skin.

Question 24

posterior column

Answer 24

consists of two tracts: the gracile fasciculus and the cuneate fasciculus. The posterior column tracts convey nerve impulses for discriminative touch, light pressure, vibration, and conscious proprioception (the awareness of the positions and movements of muscles, tendons, and joints).

Question 24

myotome:

Answer 24

Each set of spinal nerves also innervate a certain set of muscles

Question 24

spinothalamic tract

Answer 24

onveys nerve impulses for sensing pain, warmth, coolness, itching, tickling, deep pressure, and crude touch.

Question 25

motor direct pathways VS indirect pathways:

Answer 25

Motor direct pathways include the * lateral corticospinal, * anterior corticospinal, * corticobulbar tracts. They convey nerve impulses that originate in the cerebral cortex and are destined to cause voluntary movements of skeletal muscles. Motor indirect pathways include: * rubrospinal, * tectospinal, * vestibulospinal, * lateral reticulospinal, * medial reticulospinal tracts. These tracts convey nerve impulses from the brain stem to cause automatic movements and help coordinate body movements with visual stimuli. Indirect pathways also maintain skeletal muscle tone, Conduction function of the spinal cord

Question 25

causes of spinal nerve pain:

Answer 25

(when people age), the jelly like material between the discs can dry out, making them thinner, letting the vertebrae move closer to eachother. This is how they can start to pinch a nerve and cause pain where the nerve goes. - this can also happen with extra lifting

Question 25

fiber types

Answer 25

Pain can be separated into an early perception of sharp pain and a later sensation that is described as having a duller, burning quality. (A) First and second pain, as these sensations are called, are carried by different axons (B) the selective blockade of the more rapidly conducting myelinated axons that carry the sensation of first pain (C) blockade of the more slowly conducting C fibers that carry the sensation of second pain.

Question 25

anterolateral system functions:

Answer 25

The anterolateral system supplies information to different parts of the brainstem and forebrain that contribute to different aspects of the experience of pain: - Sensory discriminative aspects of pain: the location, intensity, and quality of the noxious stimulation. - Affective-motivational aspects of pain: the unpleasant feeling, the fear and anxiety, and the autonomic activation that accompany exposure to a noxious stimulus (the classic "fight-or-flight" reaction

Question 25

the anterolateral system:

Answer 25

(A) Primary afferents in the dorsal root ganglia send their axons via the dorsal roots to terminate in the dorsal horn of the spinal cord. Afferents branch and course for several segments up and down the spinal cord in Lissauer’s tract, giving rise to collateral branches that terminate in the dorsal horn. Second-order neurons in the dorsal horn send their axons (black) across the midline to ascend to higher centers in the anterolateral column of the spinal cord. (B) C-fiber afferents terminate in Rexed's laminae 1 and 2 of the dorsal horn, while Aδ fibers terminate in layers 1 and 5. The axons of second-order neurons in laminae 1 and 5 cross the midline and ascend to higher centers.

Question 26

slide 60

Answer 26

!!!!

Question 27

sensitisation:

Answer 27

Substances released by damaged tissues augment the response of nociceptive fibers. In addition, electrical activation of nociceptors causes the release of peptides and neurotransmitters that further contribute to the inflammatory response

Question 28

peripheral VS central sensitisation:

Answer 28

- Peripheral sensitization results from the interaction of nociceptors with the "inflammatory soup" of substances released when tissue is damaged. - Central sensitization refers to an immediate onset, activity-dependent increase in the excitability of neurons in the dorsal horn of the spinal cord following high levels of activity in the nociceptive afferents

Question 29

slide 62 !!

Answer 29

!! + 63 !!! + 66

Question 30

Where does the information come from?

Answer 30

RECEPTORS: - ancient - free nerve endings * invade the epithelium of the skin and mucosa, occur in the walls of viscera * no highly specialized structures around the peripheral processes of sensory neurons * pain and temperature, with relatively high threshold - relatively new - specialized structures * rather in the dermis and subcutis, in joints, muscles and tendons * complex structures around the peripheral nerve endings composed of different cell types including modified Schwann-cells * low threshold for touch, pressure, vibration, stretch

Question 31

information exchange in spinal cord:

Answer 31

slide 68 !!!

Question 32

effectors (muscles and glands)

Answer 32

CNS directly controls skeletal and visceral striated muscles through the neuromuscular junctions: there is no need for synapses on the periphery. - Direct Control via Neuromuscular Junction: The neuromuscular junction is the point where the motor neuron communicates directly with the muscle fiber by releasing the neurotransmitter acetylcholine (ACh), triggering muscle contraction.

Question 33

CNS on smooth muscles and glands:

Answer 33

Axons of autonomic neurons of the CNS terminate in autonomic ganglia and only the axons of those neurons resting in them will reach the target organs. Without at least one synapse on the periphery CNS has no direct influence on smooth muscles and glands.

Question 34

Nervous system cells: (action)

Answer 34

slide 7

Question 35

what are neurones ?

Answer 35

cells in nervous tissue neurones = charged cells, conduct electrical signals to pass information through the body

Question 36

neurons composition functions:

Answer 36

- neurons communicate with other neurons and tissues by action potential. - neurones have special processes: dendrites receive input and axons transmit action potential - some axons = coated with myelin (white sheath) - gaps in myelin = nodes of Ranvier - Similar to other cell in body having nucleus and most organelles in cytoplasm - different because: Neurons has branches or processes- dendrites and axon - Have nissl granules and neurofibrillae - No centrosome- loss power of division - Contain and secrete neurotransmitters

Question 37

efferent VS afferent neurones:

Answer 37

- efferent: * Carry impulses from CNS to peripheral effector organs e.g., muscles/glands/blood vessels * Generally each motor neurons has long axon and short dendrites - afferent: * Carry impulses from periphery to CNS * Generally each neuron has short axon and long dendrites