Nervous system: cells and sensation

Question 1

Two principle cell types for neurology

Answer 1

Neurons and neuroglial cells

Question 2

What are neurons-nerve cells

Answer 2

Are the structural and functional units of nervous system
Excitable cells that transmit electrical signals (specialized in processing information)
Cannot reproduce but can regenerate cell processes if the cell body remains intact

Question 3

What are neuroglial cells

Answer 3

They offer structural & functional support, protection, and anchor Neurons in place
Not excitable (do not generate action potentials)
Retain ability to continue dividing/reproduce

Question 4

Types of neuroglial cells for CNS

Answer 4

Microglia cells
astrocytes
ependymal cells
oligodendrocytes

Question 5

What are microglia cells

Answer 5

small, ovoid cells with spiny processes
Defence and immune-related activities (CNS phagocytes)
Play a role in the developing brain by eliminating excess/unnecessary synapses

Question 6

What are astrocytes

Answer 6

Star-shaped cells (highly branched)
Control the levels of neurotransmitter around synapses and the concentrations of important ions (K+)
Provides structural and metabolic support
Help maintain the blood brain barrier

Question 7

What are ependymal cells

Answer 7

Ciliated epithelial cells which ranges from squamous to columnar or cuboidal in shape
They line the spinal cord central canal and ventricles of the brain.
Aid production and movement of cerebrospinal fluid (CSF)

Question 8

What are oligodendrocytes

Answer 8

They usually appear as small cells with rounded, condensed nuclei and unstained cytoplasm as their processes and sheaths are not visible by routine light microscope staining
Extend many processes which wrap around axons in CNS (myelin production)
Electrical insulation in the CNS
Speed up neurotransmission

Question 9

Types of neuroglial cells PNS

Answer 9

Schwann cells and satellite cells

Question 10

What are schwann cells

Answer 10

form myelin around a portion of only one axon in the PNS
Electrical insulation in the PNS
Speed up neurotransmission

Question 11

What are satellite cells

Answer 11

Small cells that form a thin, intimate glial layer around each large neuronal cell body in the ganglia of the PNS
Structural and metabolic support for neuron cell

Question 12

What is Excitotoxicity

Answer 12

It is defined as cell death resulting from the toxic actions of excitatory amino acids.

Question 13

What is neuronal excitotoxicity

Answer 13

Neuronal excitotoxicity usually refers to the injury and death of neurons arising from prolonged exposure to glutamate and the associated excessive influx of ions into the cell
Glutamate is the major excitatory neurotransmitter in the CNS

Question 14

The activation of what exerts the excitatory effects of glutamte

Answer 14

3 major types of ionotropic receptors (NMDA, AMPA and KA)
several classes of metabotropic receptors linked to G-proteins

Question 15

What are NMDA receptors

Answer 15

NMDA receptors are Ca2+ favouring glutamate-gated ion channels that are expressed in most central neurons

Question 16

What happens when excessive activation of NMDA receptors

Answer 16

Excessive activation leads to Ca2+ overload and catabolic enzyme activities, triggering a cascade of events culminating in apoptosis or necrosis

Question 17

Describe sensory receptors and what they monitor

Answer 17

The nervous system monitors somatic and visceral environments to maintain proper functions of the body.
Sensory information is acquired at the terminal end of spinal and cranial sensory nerve fibres and is conveyed to the CNS for further processing.
Some sensory information is consciously detectable, enabling animals to feel pain, touch, temperature, and a full bladder as well as see and taste.
Other information does not reach conscious levels such as blood pressure and the levels of oxygen and carbon dioxide in the blood.
The sensory signals are carried by various ascending tracts to the thalamus, which then projects to the somatosensory cortex.

Question 18

What are 3 categories of the properties of sensory receptors

Answer 18

Free nerve endings, encapsulated nerve endings, specialised receptors

Question 19

What are free nerve endings sensory receptors

Answer 19

Receptors with no special modifications, their terminal ends form numerous branches in target tissues
Are receptors for somatic and visceral sense of pain (nociceptors) and temperature (thermoreceptors)

Question 20

What are encapsulated nerve endings

Answer 20

Sensory terminals are ensheathed by a connective tissue capsule
Found mainly in the inner dermis, fasciae, mesenteries, skeletal muscles, and some viscera
All encapsulated endings are mechanoreceptors.

Question 21

What are specialised receptors

Answer 21

Distinct structural components which are adapted to interpret specific stimulus – e.g., photoreceptors – light

Question 22

Describe mechanoreceptors

Answer 22

Are a type of somatosensory receptors which relay extracellular stimulus to intracellular signal transduction through mechanically gated ion channels.
The external stimuli are usually in the form of touch, pressure, stretching, sound waves, and motion.

Question 23

Where are mechanoreceptors

Answer 23

They are present in the skin, ears and musculoskeletal system.
These receptors are either encapsulated (mostly) or unencapsulated

Question 24

General divisions of mechanoreceptors

Answer 24

Tactile
Allow for differential detection of touch and vibrational stimuli that permit detection of benign or harmful pressure.
Proprioceptors
Are essential for awareness of kinesthesis (i.e., joint position direction and velocity of joint movements)

Question 25

Describe photoreceptors

Answer 25

Photoreceptor cells are adapted to respond to light stimulus

Question 26

Where are photoreceptors

Answer 26

They are found in the innermost layer of the eye, the retina.

Question 27

Two types of photoreceptors cells

Answer 27

Rods Are sensitive to low light levels but not to colour; they provide black and white and night vision. Cones Are sensitive to bright light; they provide colour vision.

Question 28

What are chemorecptors

Answer 28

Stimulated by chemical substnaces

Question 29

Where are chemoreceptors found

Answer 29

Examples of where they are found in the body including the nose (olfaction/smell), tongue (taste), and blood vessels (pH, CO₂)

Question 30

Chemoreceptors in carotid body

Answer 30

Chemoreceptors in the carotid body are sensitive to changes in arterial tension of oxygen (PaO2) and carbon dioxide (PaCO2).

Question 31

Chemoreceptors in taste buds

Answer 31

Taste buds are stimulated by chemical molecules dissolved in the mucus/saliva in the oral cavity Each taste bud consists of receptor or gustatory cells surrounded by sustentacular or supporting cells located in various types of papillae (e.g., dog – fungiform, vallate, and foliate) Can differentiate between different tastes by detecting interaction with different molecules or ions

Question 32

Chemoreceptors in olfactory receptor cells

Answer 32

Olfactory receptor cells are rod-shaped bipolar neurons, found in the caudal part of the nasal cavity. Chemicals responsible for smell dissolve in the mucus of the nasal cavity and stimulate the production of nerve impulses.

Question 33

Describe thermoreceptors

Answer 33

They are preferentially receptive to cold or to warm stimuli They function to detect heat and cold, contributing to thermoregulation

Question 34

Where are thermoreceptors found

Answer 34

They are found peripherally and centrally peripheral thermoreceptors are located in the skin and sense surface temperatures, central thermoreceptors are found in the viscera, spinal cord, and hypothalamus and sense the core temperature

Question 35

Describe nociceptors

Answer 35

Are receptors for both somatic and visceral sense of pain

Question 36

Describe nociceptors somatically

Answer 36

In somatic structures they detect changes caused by damaging stimuli

Question 37

Describe nociceptors

Answer 37

In viscera they detect changes caused by abnormal physical conditions (e.g., gastrointestinal bloating or cramping) or pathological conditions (e.g., peritonitis, pericarditis). Visceral organs are not sensitive to cutting, heat or cold, but they respond to stretching, distension, spasm, inflammation, or ischemia. Visceral pain is poorly localised.

Question 38

Describe physiologic receptors

Answer 38

Are a type of viscerosensory receptors composed of free nerve endings They respond to innocuous stimuli. E.g., the baroreceptors located in the carotid sinus and aortic arch respond to changes in blood pressure.

Question 39

What do physiologic receptors do

Answer 39

These sensory receptors trigger normal visceral reflexes to regulate heart rate and respiration. Some free nerve endings in the respiratory epithelium are sensitive to inhaled particles in the respiratory airways. The coughing reflex, for example, is triggered by these receptors. Other physiologic receptors are located in the smooth muscle layer of the viscera. They respond to stretch or tension. Their sensory signals are important for a sense of fullness in certain organs (e.g., stomach, large intestine, urinary bladder), gastrointestinal motility, micturition and defecation.

Question 40

List some animal species differences of sensory perceptio

Answer 40

Different colour vision: bees(UV light) reptiles(infra red), some have magnetoreceptors like migratory birds, and electrorecptors in fish, canine have a better hearing and smell while we can see more coloured vision. also monocular vs binocular. also animals have a range of frequency they can hear, like dogs have higher than us, bats even higher and dolphins and fish even higher.

Question 41

Describe basic sensory receptor

Answer 41

Sensory receptor detects stimulus Converts this into action potential in sensory afferent neuron of the PNS Travels to the CNS Processed in CNS (not always consciously) Travels to the skeletal muscle via PNS motor efferent neuron