nerve system

Question 1

define Central Nervous System (CNS)

Answer 1

brain and spinal cord

Question 2

How can you classify peripheral nerves?

Answer 2

1. origin of nerve ( cranial or spinal)
2. direction of impulse propagation ( sensory or motor neurons)
3. target effector organ ( somatic or autonomic nervous system)

Question 3

define Peripheral Nervous System (PNS)

Answer 3

ganaglia and peripheral nerves (cranial and spinal)

Question 4

define cranial nerve

Answer 4

emerge from the brain or brain stem.
There are 12 pairs

Question 5

define spinal nerve

Answer 5

emerge from the spinal cord.
There are 31 pairs

Question 6

define sensory (afferent) neurons

Answer 6

transmit impulses from sensory organs to the CNS.

Question 7

define motor (efferent) neurons

Answer 7

transmit impulses from CNS to effectors organs

Question 8

define somatic nervous system (SNS)

Answer 8

direct the contraction of skeleton muscles.

Question 9

define autonomic nervous system (ANS)

Answer 9

controls the activities of the organs, glands and involuntary muscles.
contains 2 parts: sympathetic and parasympathetic.

Question 10

What is the purpose of the peripheral nervous system?

Answer 10

• relay information to the CNS
• execute motor function

Question 11

define neurons

Answer 11

The fundamental unit of the nervous system

Question 12

define soma

Answer 12

the body of the cell
has all the cell’s organelles
has a lot of nissl bodies.

Question 13

define nissl bodies

Answer 13

rER with a lot of ribosomes on it.
The primary function of Nissl bodies is protein synthesis. The abundant ribosomes within them actively produce various proteins essential for neuronal function (neurotransmitters).

Question 14

define axon

Answer 14

-the transmitting element of the neuron
-thin (0.2-20 micrometer)
-long (0.1mm-2m)
-has microtubules (for it’s tunic shape and carry)
- has a lot of mitochondria
-contains neurofilaments

Question 15

define axoplasm

Answer 15

Cytoplasm in the Axon

Question 16

define axolemma

Answer 16

the membrane who wraps the axon

Question 17

define axon hillock

Answer 17

-the area in which the soma turns to the axon.
- no free ribosomes & rER

Question 18

define initial segment

Answer 18

-electricity starts from this area
there starts the action potential (trigger zone) and the impulse starts to conduct.

Question 19

define axon terminals

Answer 19

• the end of the axon
• have bulbs (boutons) in the bottom that contain neurotransmitters

Question 20

have many axons can each neuron have?

Answer 20

only 1!

Question 21

define dendrites

Answer 21

• an extension of the cell body (branch out - each bramch is a spine)
• main apparatus used to receive incoming signals from other nerve cells and transmit the information to the soma.
• increase surface area
• have spines that form the post synaptic contact site that receive signals
• composed of neurofilament (make their shape)

Question 22

define myelin

Answer 22

• the protector of the axon
• forms an inconsistent fatty layer around the axon
• sometimes protects the dendrites
• built from sphingolipids (80%) and proteins

Question 23

define synapses

Answer 23

the space between a presynaptic neuron and a postsynaptic neuron. the site at which signals are transmitted.

Question 24

define synaptic transmission

Answer 24

presynaptic neuron (transmits) to the synapthic cleft (the space in which transmission done) to postsynaptic neuron (receives)

Question 25

classification of neurons according to function

Answer 25

sensory neurons (afferent neurons)- starts in peripheral nerves and end toward CNS.
- activated by physical inputs or by chemical signals

motor neurons (efferent neurons)- starts in the CNS and transfer information towards the peripheral parts ( to the effectors- capable of a response)
- have many branched dendrites
- have extremely long axons

interneurons- located in the CNS, they get information from the sensory neurons, process it and can decide if to transfer it to the motor neurons.

Question 26

define nodes of Ranvier
what is the size of the gap?

Answer 26

-the spaces between myelin
- help move action potential along
- Not all of the axons contain them
the gaps are 1-2 um
they have an impact on the speed of transmission.

Question 27

classification of neurons according to structure

Answer 27

multipolar neurons
-usually have one axon
-several to numerous dendritic structures emerging at various points along the cell body
-usually are motor neurons
- have different shapes (length of axons, dimensions and intricacy of their dendritic branching patterns)

bipolar neurons
-have oval somas
-2 distinct processes : a single dentritic structure that receives signals and an axon that carries information toward the CNS.
-mostly sensory neurons
-pseudo-unipolar cells: variants of bipolar cells

unipolar neurons
-simplest structure
- in vertebrates are primarily sensory neurons (found in the ANS)

pseudounipolar
mostly sensory neurons

Question 28

define Neuroglia

Answer 28

• Cells in the CNS
• greatly outnumber neurons (2-10 times more )
• surround the cell bodies , axons and dendrites of neurons
• In vertebrate nervous system can Le divided to:
  Micreglia & macroglia

Question 29

what is the parasymapthetic system?

Answer 29

The parasympathetic nervous system (PNS), often referred to as the “rest and digest” system, is one of the two branches of the autonomic nervous system (ANS).
The PNS promotes a state of relaxation and stimulates bodily functions that conserve energy and promote bodily processes like digestion, waste elimination, and cell renewal

Question 30

what is the symapthetic system?

Answer 30

The sympathetic nervous system (SNS), also known as the “fight-or-flight” system, is one of the two branches of the autonomic nervous system (ANS) that regulates various involuntary bodily functions.
The SNS mobilizes the body’s resources to prepare for physical exertion or stressful situations

Question 31

define neurotransmitters

Answer 31

chemical that can be released by exocytosis upon the arrival of the action potential within the area.

Question 32

where Ca+2 is storged in the neuron? and how it is used?

Answer 32

it is storged in the sER in the synapthic bulbs.
they are needed to transmit the action potential.
When a neuron receives an electrical signal, voltage-gated calcium channels in the plasma membrane (outer membrane of the neuron) open.
This opening allows calcium ions to rapidly flow into the cytoplasm from the high-concentration store in the SER.
The sudden rise in cytosolic calcium concentration triggers neurotransmitter release.

Question 33

what are the 4 macroglia? and what are their functions?

Answer 33

**Astrocytes: star-shaped glial cells are the most abundant cell type in the CNS. They are providing nutrients and oxygen to neurons, helping to regulate the chemical environment around neurons, supporting and insulating neurons, playing a role in the blood-brain barrier.

**Oligodendrocytes:These glial cells are responsible for producing myelin, a fatty substance that insulates nerve fibers in the CNS. Myelin helps to speed up the transmission of nerve impulses.

**Schwann cells: Similar to oligodendrocytes in the CNS, Schwann cells myelinate neurons in the PNS. They wrap around individual nerve fibers, forming a myelin sheath that insulates the axon and speeds up the transmission of nerve impulses.

**Ependymal cells:These cells line the ventricles of the brain and spinal cord, which are cavities filled with cerebrospinal fluid. Ependymal cells help to produce cerebrospinal fluid and regulate its flow.

Question 34

what is microglia?

Answer 34

Microglia are the resident immune cells of the central nervous system (CNS), acting as its first and main line of defense.

Question 35

what is the difference between microglia and macroglia?

Answer 35

Microglia are much smaller than macroglia, hence the “micro” prefix.
Microglia are classified as immune cells, while macroglia primarily provide structural and metabolic support to neurons.

Question 36

describe the annatomy of a nerve

Answer 36

Many axons from various neurons come together to form a nerve. These axons are wrapped in several layers of connective tissue, providing structure and protection:

**Endoneurium: This is a thin, delicate layer that surrounds each individual axon.
**Perineurium: This layer groups bundles of axons, called fascicles, together.
**Epineurium: The outermost layer, made of tough connective tissue, binds the entire nerve fascicles together.

Question 37

what’s the princple of dynamic polarization?

Answer 37

it describes the hypothesized one-way flow of nerve impulses in a neuron. According to this law, dendrites and the cell body receive signals, the axon conducts the signal, and the terminal arborizations of the axon transmit the signal to other neurons.

Question 38

what’s the princple of connectional specificty?

Answer 38

It states that:
Neurons don’t form connections indiscriminately with just any other neuron they come across. Instead, they connect with specific target neurons in a precise and ordered manner.
and that each neuron communicates only with certain postsynaptic targets (the receiving neuron) and not with others. These connections occur at specialized points of contact called synapses.

Question 39

what is a fascicle?

Answer 39

some nerve fibers (axons) in one unit.

Question 40

what is excitatory signal?

Answer 40

a signal that make the the next cell active.

Question 41

what is inhibitory signal?

Answer 41

a signal that make the the next cell NOT active.

Question 42

what is action potential?

Answer 42

An action potential is an electrical event that travels along the axon of a neuron. It’s the fundamental unit of communication in the nervous system, responsible for transmitting information between neurons and to target cells.

Question 43

what is resting potential? what is the charge?

Answer 43

Neurons maintain a voltage difference across their cell membrane, called the resting potential. The inside of the neuron is negatively charged compared to the outside. This difference is due to unequal distribution of ions (charged particles) on either side of the membrane.
the charge is negative 70 mili volt.

Question 44

what’s Depolarization?

Answer 44

when the action potential gets triggered.
If a stimulus (like an excitatory neurotransmitter binding to receptors) is strong enough, it causes certain ion channels to open. These channels are typically voltage-gated sodium (Na+) channels.
Sodium ions rush into the cell due to their concentration gradient (higher outside, lower inside). This influx of positive charges depolarizes the membrane, meaning the voltage difference between inside and outside gets smaller (becomes less negative).

Question 45

what’s Repolarization? after how much time does it begin?

Answer 45

This is the recovery phase where the neuron resets itself.
As the action potential reaches its peak, voltage-gated sodium channels close, and voltage-gated potassium (K+) channels open.
Potassium ions, with a higher concentration inside the cell, flow out rapidly, restoring the resting membrane potential.
it begins after 1 ms.

Question 46

what is NA+ and K+ pump?

Answer 46

The sodium-potassium pump (Na+/K+ pump), also known as the sodium-potassium adenosine triphosphates (Na+/K+-ATPase), is an integral membrane protein found in all animal cells. It is an active transport protein that uses energy from ATP to move sodium ions (Na+) out of the cell and potassium ions (K+) into the cell against their concentration gradients. This process is essential for maintaining a stable resting membrane potential, regulating cell volume, and transporting various molecules across the cell membrane.

Question 47

how the resting membrane potential is created?

Answer 47

The resting membrane potential, the voltage difference across a neuron at rest, is created by the interplay of two main factors:

Unequal distribution of ions: Different concentrations of charged particles (ions) exist on either side of the neuronal cell membrane. The key players are:
Sodium (Na+) ions are more concentrated outside the cell than inside. Potassium (K+) ions are more concentrated inside the cell than outside.
Large anions (protein and other negatively charged molecules) are stuck inside the cell due to their size and contribute to the negative charge on the inner side.
the sodium-potassium pump (Na+/K+ pump) actively transports Na+ ions out of the cell and K+ ions into the cell against their concentration gradients.

Selective permeability of the membrane: The phospholipid bilayer of the cell membrane acts as a selective barrier. It allows some ions to pass through more easily than others. Potassium channels are “leak” channels, meaning they are always somewhat open and allow K+ ions to move down their concentration gradient, flowing out of the cell.

Question 48

what is the charge of the active potential?

Answer 48

+40 mV

Question 49

what are the phases of action potential?

Answer 49

Resting Phase
Depolarization
Repolarization
hyperpolarization
Refractory Period

Question 50

what is the refractory period?

Answer 50

This is a brief period immediately following the action potential where the neuron is less responsive to further stimulation.

Question 51

what’s hyperpolarization?

Answer 51

Hyperpolarization refers to a change in a cell’s membrane potential that makes it more negative.
Hyperpolarization occurs when this negative charge on the inner side of the membrane becomes even greater than the beginning.

Question 52

what is threshold potential?

Answer 52

As the graded potential increases (becomes less negative due to influx of positive ions), it approaches a critical value known as the threshold potential. This threshold is typically around -55 mV in neurons.
The threshold potential ensures that an action potential is either generated entirely or not at all. This allows for reliable and efficient signal transmission within the nervous system.

Question 53

what do affect the speed of AP transmission?

Answer 53

1. Axon Diameter:
   Larger diameter, faster speed - Axons with a larger diameter have a lower internal resistance to the flow of ions. This allows for faster propagation of the action potential down the axon, similar to how wider pipes allow for faster water flow.
2. Myelin Sheath:
   Presence of myelin, significant speed increase: Myelin wraps around the axon like a segmented sheath. This insulation disrupts the continuous flow of ions along the membrane, forcing the action potential to jump from one node of Ranvier (the gaps between myelin segments) to the next in a saltatory conduction process. This saltatory conduction significantly increases the speed of action potential propagation compared to unmyelinated axons.
3. axon length - the longer is the axon length the faster the transmission.

Question 54

what are the two main classes of neurotransmitters ?

Answer 54

small organic molecules - acetylcholine, amino acids, GABA, glutamine acid, biogenic amines (dopamine, serotonin).
Neuroactive peptides - hormones and peptides.

Question 55

what activity does the neurotransmitter acetylcholine generate?

Answer 55

acetylcholine acts as a chemical messenger in many parts of the nervous system, influencing muscle movement (muscles contract), cognitive functions, and various bodily processes.

Question 56

what activity does the neurotransmitter GABA generate?

Answer 56

Unlike acetylcholine, which excites certain neurons, GABA (gamma-aminobutyric acid) is the main inhibitory neurotransmitter in the central nervous system (CNS). This means it doesn’t directly generate activity, but rather reduces the firing of neurons.

Question 57

what are the differences between gray and white matter? (function, composition and location)

Answer 57

Composition:
Grey matter is packed with neuronal cell bodies. It also contains dendrites and synapses.
White matter is composed mainly of myelinated axons.

Function:
Grey matter is the powerhouse for processing information. It’s where all the heavy lifting of thought, memory, emotion, and sensory perception happens.
White matter is the information highway. It efficiently carries signals between different regions of grey matter, allowing for communication and coordination throughout the brain and spinal cord.

Location:
Grey matter is generally forms the outer layer of the brain and the butterfly-shaped center of the spinal cord.
White matter is found deeper within the brain and encasing the outer regions of the spinal cord.

Question 58

what are Menings? and what are the layers of that?

Answer 58

The meninges are three protective membranes that surround and cushion the brain and spinal cord.

The meninges consist of three distinct layers:
Dura Mater (Tough Mother): This is the outermost and strongest layer, closest to the skull and spine. It’s a fibrous membrane that provides a sturdy barrier and anchors the meninges to the bone.
Arachnoid Mater (Spider Mother): The middle layer, it’s a delicate, web-like membrane with a space beneath it called the subarachnoid space. This space contains cerebrospinal fluid (CSF), a clear, watery fluid that cushions the brain and spinal cord, absorbs shock, and helps remove waste products.
Pia Mater (Gentle Mother): The innermost layer, it’s a thin membrane that closely follows the contours of the brain and spinal cord. It contains blood vessels that nourish the nervous system tissues.

Question 59

what is the largest part of the brain?

Answer 59

cerebrum (85%)

Question 60

what are the hemispheres? how are they connected?

Answer 60

the brain is divided into two halves called cerebral hemispheres, right and left. They are connected by a thick band of nerve fibers called the corpus callosum which allows them to communicate with each other.

Left hemisphere: Language processing, logic, analytical thinking, mathematics, and some motor skills.
Right hemisphere: Spatial awareness, creativity, facial recognition, music, and emotions.

Question 61

what are the convolutions in the brain?

Answer 61

The convolutions in the brain, also known as gyri ,sulci and fissure are folds in the folded outer layer of the brain called the cerebral cortex.
Gyri are the raised, winding folds that make the characteristic wrinkled appearance of the brain.
Sulci are the grooves or furrows between the gyri.
Fissures are deeper grooves that separate larger lobes of the brain.

Question 62

what are the 4 lobes?

Answer 62

Frontal Lobe: Located in the front of the brain, the frontal lobe is associated with higher-order functions such as planning, problem-solving, decision-making, judgment, and language production.

Parietal Lobe: Situated behind the frontal lobe, the parietal lobe is involved in processing sensory information from the body, including touch, taste, and temperature. It also plays a role in spatial awareness, navigation, and body image.

Temporal Lobe: Found on the side of the brain just above the ears, the temporal lobe is crucial for processing auditory information, including hearing and music perception. It’s also involved in memory, emotion, and speech comprehension.

Occipital Lobe: Located at the back of the brain, the occipital lobe is the primary area for visual processing. It receives and interprets visual information from the eyes.

Question 63

what is the broca’s area?

Answer 63

Broca’s area, also sometimes referred to as the Broca area, is a region in the frontal lobe of the dominant hemisphere (usually the left hemisphere) of the brain. It’s particularly important for speech production.

Question 64

what is the prefrontal cortex?

Answer 64

The prefrontal cortex (PFC) is the area at the forefront of the frontal lobe of the brain. It’s responsible for many higher-order executive functions, including: Planning and decision-making, Working memory ,Problem solving, Judgment, Impulse control, Emotional regulation, Social behavior.

Question 65

what is the primary motor cortex?

Answer 65

The primary motor cortex is a region of the brain located in the frontal lobe that plays a critical role in initiating voluntary movements.

Question 66

what is the primary somatosensory cortex?

Answer 66

The primary somatosensory cortex is a crucial region in the brain responsible for processing information from throughout the body. It’s located in the postcentral gyrus of the parietal lobe, just posterior (behind) to the central sulcus.

Question 67

what is the Wernicke’s area?

Answer 67

Wernicke’s area, also sometimes called Wernicke’s speech area, is a region in the brain crucial for language comprehension. It’s located in the temporal lobe, typically on the left side of the brain for most people.

Question 68

what is the cerebral cortex?

Answer 68

The cerebral cortex is the thin outer layer of your brain that is composed of gray matter and responsible for most of the thinking, feeling, and sensory experiences. It’s like the brain’s control center for activities like language, memory, and movement.

Question 69

what is the basal nuclei?

Answer 69

The basal ganglia, also sometimes referred to as the basal nuclei, are a pockets of gray matter located deep within the brain that play a critical role in movement control, emotions and learning.

Question 70

what is the Diencephalon? what are the main structures in it?

Answer 70

The diencephalon, also sometimes referred to as the interbrain, is a crucial region located deep within the brain. It acts as a central hub that relays information between different parts of the brain and plays a vital role in various functions.

The diencephalon is composed of four main structures, each with specific functions:
-Thalamus: Often referred to as the “gateway” to the cortex, the thalamus relays sensory and motor signals to different parts of the brain. It also plays a role in sleep, alertness, and memory.
-Hypothalamus: This tiny structure acts as the control center for many autonomic functions like body temperature regulation, hunger, thirst, sleep-wake cycles, and hormone release.
-Epithalamus: Contains structures involved in regulating sleep and some sensory functions, including the pineal gland which produces melatonin (a hormone influencing sleep-wake cycles).
-Subthalamus: Plays a role in motor control and movement coordination, working with the basal ganglia (another group of structures deep within the brain).

Question 71

what is the Hypothalamus?

Answer 71

tiny structure that acts as the control center for many autonomic functions like body temperature regulation, hunger, thirst, sleep-wake cycles, and hormone release.

Question 72

what is the brainstem? what are its regions?

Answer 72

The brainstem is located at the base of the brain and connects the cerebrum (the largest part of the brain) to the spinal cord. It acts as a vital control center for many automatic functions essential for survival.

The brainstem is further divided into three sections:
Midbrain: Located at the uppermost part of the brainstem, it’s involved in relaying sensory information, movement coordination, and alertness.
Pons (bridge): Acts as a bridge between the two hemispheres of the brain and relays information between the brain and cerebellum. It’s also involved in sleep regulation and facial movements.
Medulla oblongata: The lowermost part of the brainstem, it controls many vital autonomic functions like breathing, heart rate, and blood pressure.

Question 73

what is the limbic system? what are its components?

Answer 73

The limbic system is a group of interconnected brain structures involved in emotional responses, motivations, behavior, learning, and memory. It’s often referred to as the brain’s emotional center and plays a crucial role in shaping our experiences and interactions with the world.

Amygdala - the “fear center”
Hippocampus- It helps us convert short-term memories into long-term memories.
Cingulate cortex: Plays a role in processing emotions, memory, and learning.

Question 74

what are the ventricles of the brain? what are four main ventricles?

Answer 74

The ventricles of the brain are a network of interconnected cavities filled with cerebrospinal fluid (CSF) that reside deep within the brain. They play a vital role in protecting the brain tissue, cushioning it from impacts, and helping to remove waste products.

There are four main ventricles in the brain:
-Lateral ventricles: The largest pair of ventricles, located within each cerebral hemisphere. They appear somewhat like butterfly wings in shape.
-Third ventricle: A narrow cavity situated in the diencephalon, between the two thalamus structures.
-Fourth ventricle: Located at the back of the brainstem, wedge-shaped and extending down to the central canal of the spinal cord.

Question 75

what are the choroid plexus?

Answer 75

The choroid plexus are highly vascular structures located within the ventricles of the brain. They are essential for producing cerebrospinal fluid (CSF)

Question 76

what is the blood-CSF barrier?

Answer 76

The blood-CSF barrier (BCSFB) is a highly selective filtering system that separates the bloodstream from the cerebrospinal fluid (CSF) surrounding the brain and spinal cord. It acts as a security checkpoint, meticulously controlling the passage of substances between the blood and the delicate neural tissue.
it’s formed by the tight junctions between epithelial cells lining the choroid plexus.

Question 77

what is the blood-brain barrier? how is it established?

Answer 77

The blood-brain barrier (BBB) is a fascinating and critical protective system in your brain. It acts as a highly selective gatekeeper, meticulously controlling what substances can pass from your bloodstream into the fluid surrounding your brain and spinal cord (cerebrospinal fluid, CSF).
the BBB allows essential nutrients like glucose (your brain’s primary fuel) and oxygen to pass and prevents harmful substances like heavy metals, pollutants, bacteria, and viruses from entering.

it is established by:
Tight Junction Formation
Astrocyte Involvement
basal lamina

Question 78

what is the spinal column? how are the vertebrae organized?

Answer 78

It’s a long, flexible column made up of individual bones called vertebrae, stacked on top of each other and connected by ligaments and joints.

generally categorized into five regions based on their location and structure:
-Cervical vertebrae (C1-C7): These are the seven vertebrae in the neck region. They are the smallest and most flexible vertebrae, allowing for a wide range of head movement. The first two cervical vertebrae (C1 and C2) are unique and specialize in head articulation with the skull.
-Thoracic vertebrae (T1-T12): The twelve vertebrae in the chest region. They are larger and sturdier than cervical vertebrae and connect to the ribs, forming the rib cage that protects the heart and lungs.
-Lumbar vertebrae (L1-L5): These five vertebrae are located in the lower back and are the largest and strongest vertebrae due to the weight they bear. They provide support for the lower body and allow for significant bending and twisting movements.
-Sacral vertebrae (S1-S5): It’s located at the base of the spine (hips). The sacrum is a triangular-shaped bone formed by the fusion of five sacral vertebrae in adulthood.
-Coccyx (tailbone): The coccyx is a small, triangular bone at the very bottom of the spinal column, formed by the fusion of four coccygeal vertebrae. It has limited mobility and vestigial function in humans.

Question 79

what are the functions of the spinal cord?

Answer 79

-Conducts Nerve Impulses:
The spinal cord serves as a communication cable, relaying messages between the brain and the body. Sensory information travels from the body through sensory neurons to the spinal cord. The brain sends motor commands down the spinal cord through motor neurons.

-Reflex Coordination:
It has the remarkable ability to coordinate certain reflexes without involving the brain. These reflexes are involuntary, rapid responses to stimuli that help protect the body from harm or maintain homeostasis (internal balance).

Question 80

what are roots in the spinal nerves? and what are the types of Spinal Nerve Roots?

Answer 80

roots refer to the two bundles of nerve fibers that come together to form a single spinal nerve.

-Dorsal Root (Posterior Root):
Carries sensory information towards the brain.
Emerges from the posterior (dorsal) horn of the gray matter in the spinal cord.
Made up of sensory axons.
The dorsal root has a swelling called the dorsal root ganglion (sensory ganglion). This swelling contains the cell bodies of sensory neurons, where the sensory fibers originate.

-Ventral Root (Anterior Root):
Carries motor information away from the brain.
Emerges from the anterior (ventral) horn of the gray matter in the spinal cord.
Consists of motor axons.
The ventral root appears thinner and lacks a swelling compared to the dorsal root.

Question 81

what is the central canal?

Answer 81

The central canal is a tiny fluid-filled tube running lengthwise in the center of the spinal cord. It’s a remnant of the embryonic neural tube and contains cerebrospinal fluid (CSF) that helps cushion the spinal cord.

Question 82

what are dermatomes?

Answer 82

Dermatomes are areas of skin that correspond to specific spinal nerves. Each spinal nerve has a designated dermatome, and when that nerve is stimulated, you feel sensation in the corresponding area of skin. They are like a map of the body on your skin, created by the nerves that supply sensation to those regions.

Question 83

do the cranial nerves have roots?

Answer 83

no

Question 84

what’s a Ganglion? they are found in the CNS or PNS?

Answer 84

a ganglion is a small, rounded structure that acts as a cluster of nerve cell bodies outside the central nervous system (CNS). These cell bodies are essentially the “engines” of neurons, containing the nucleus and other essential components for neuronal function. Ganglia are found throughout the peripheral nervous system (PNS), which relays information between the CNS (brain and spinal cord) and the rest of the body.

Question 85

what’s a dorsal root Ganglion? what kind of neurons it consists?

Answer 85

A dorsal root ganglion (DRG), also known as a spinal ganglion, is a cluster of nerve cell bodies located on the dorsal (back) root of each spinal nerve. It’s a crucial structure in the peripheral nervous system (PNS) that plays a vital role in sensation.
it consists pseudo-unipolar neurons.

Question 86

what is the difference between central process and peripheral process?

Answer 86

Central Process (Central Axon):
It carries the processed sensory information away from the soma towards the brain.

Peripheral Process (Peripheral Axon and Dendrites):
Carries the initial, unprocessed sensory information from the environment or internal organs towards the central nervous system (CNS).

Question 87

what’s a reflex?

Answer 87

A reflex is an involuntary and unplanned and predictable motor respond to a sensory stimulus. It’s an automatic response that happens very quickly, without any conscious thought or decision-making involved. Reflexes are essential for protecting your body from harm and maintaining homeostasis (internal balance).

Question 88

what’s a reflex arc? they are belonged in the CNS or PNS? what are its components? what kind of feedback?

Answer 88

The pathway a reflex takes is called a reflex arc. in the PNS. it’s a negative feedback.

It involves several key players:
-Sensory receptor: This detects the stimulus.
-Sensory neuron: Carries a signal from the receptor to the spinal cord.
-Spinal cord: Acts as the control center, processing the sensory information.
-integration center
-Motor neuron: Transmits a signal from the spinal cord to the muscle or the gland.
-effector: organ capable of responding to the signal, resulting in the reflex action.

Question 89

what’s a interneuron?

Answer 89

an interneuron is a critical player acting as a middleman between sensory and motor neurons. interneurons communicate and process information within the CNS, specifically within the brain and spinal cord.

Question 90

what is the difference between mono and poly synaptic reflex? explain.

Answer 90

The key difference between monosynaptic and polysynaptic reflexes lies in the number of synapses involved in the reflex arc.

Monosynaptic Reflex:
Involves only one synapse between the sensory neuron and the motor neuron. This allows for a very quick reflex response, as there’s minimal delay in signal transmission.

Polysynaptic Reflex:
More Complex and Slower: Involves multiple synapses (two or more) within the CNS, typically involving interneurons in addition to the sensory and motor neurons. This allows for more complex processing and integration of information before triggering a motor response.

Question 91

what is the pituitary gland?

Answer 91

The pituitary gland, also sometimes called the hypophysis, is located at the base of the brain. It’s a critical player in the endocrine system, often referred to as the “master gland” because it produces and secretes several hormones that regulate various bodily functions.

Question 92

what are autonomic reflexes?

Answer 92

autonomic reflexes are involuntary motor responses triggered by the autonomic nervous system (ANS) in response to internal stimuli. Unlike skeletal reflexes, which involve conscious muscle movement, autonomic reflexes regulate the body’s unconscious functions like heart rate, digestion, and pupil dilation.

Question 93

what are preganglionic neuron and postganglionic neuron? ANS

Answer 93

Preganglionic neurons and postganglionic neurons are two distinct types of neurons that work together within the autonomic nervous system (ANS) to regulate various involuntary bodily functions.

Preganglionic Neurons:
They are carrying signals from the central nervous system (CNS) to the autonomic ganglia.
Primarily release acetylcholine (ACh) at the synapse with postganglionic neurons.

Postganglionic Neurons:
They are transmitting signals from the autonomic ganglia to the target organs (muscles, glands, etc.).
The type of neurotransmitter released by postganglionic neurons varies depending on the branch of the ANS and the target organ.

(Sympathetic nervous system (SNS): Primarily uses norepinephrine (noradrenaline) at the target organ.
Parasympathetic nervous system (PNS): Primarily uses acetylcholine (ACh) at the target organ, but some exceptions exist.)

Question 94

what is autonomic ganglia?
what are the 3 kinds? (classification by location)

Answer 94

Autonomic ganglia, also known as simply ganglia in the context of the autonomic nervous system (ANS), are clusters of nerve cell bodies (somata) located outside the central nervous system (CNS). They act as crucial communication hubs within the ANS pathway, relaying signals between the CNS and various organs responsible for involuntary bodily functions.

-Paravertebral ganglia (sympathetic chain ganglia): Situated on either side of the spinal cord, these ganglia form the core of the sympathetic nervous system.
-Prevertebral ganglia (collateral ganglia): Found closer to the organs they innervate, these ganglia can be part of either the sympathetic or parasympathetic system depending on their specific location and function.
-terminal (intramural) ganglia - belong to parasympathetic system, located very very close to the target organ.

Question 95

what are the differences between parasympathetic and sympathetic ganglia?

Answer 95

The key differences between parasympathetic and sympathetic ganglia lie in their location,
and neurotransmitter usage.

Location:
Parasympathetic ganglia is generally situated closer to the target organs they innervate. This allows for more localized control over specific functions.
Sympathetic ganglia is typically located in a chain along either side of the spinal cord, forming the sympathetic trunk. Short branches connect this chain to spinal nerves. This centralized organization allows for a broader influence on various organs throughout the body.

Neurotransmitter:
Parasympathetic ganglia: Primarily use acetylcholine (ACh) as the neurotransmitter released by their postganglionic neurons.
Sympathetic ganglia: Primarily use norepinephrine (noradrenaline) as the neurotransmitter released by their postganglionic neurons.

Question 96

in what system the preganglionic fibers are longer?

Answer 96

parasympathetic nervous system (PNS)

Question 97

what is the neurotransmitter in the ganglia?
what is the neurotransmitter in the effector?

Answer 97

-Both PNS and SNS: In the ganglia (clusters of nerve cell bodies), regardless of the branch, the neurotransmitter released by the preganglionic neuron is almost always acetylcholine (ACh).

-In the Effector:
*Parasympathetic Nervous System (PNS): The neurotransmitter released at the target organ (effector) in the parasympathetic system is typically acetylcholine (ACh).
*Sympathetic Nervous System (SNS): The neurotransmitter released at the target organ in the sympathetic system is usually norepinephrine (noradrenaline).