Skin and nervous system exam

4 functions of skin

Sensory Organ, Protection, Regulates Body Temp, Vitamin D absorption

How is skin a sensory organ?

neuroreceptors (e.g. pain, touch)

How does skin provide protection?

barrier (water proof, blocks microbes

How does skin regulate body temp?

body heat to surface (radiation, sweating)

What is skin’s role with Vitamin D

it absorbs (UVB) essential for bones and immune system

What are the 3 layers of the skin?

Epidermis, Dermis, Hypodermis

Epidermis

Outermost layer of skin

What kind of cells is the epidermis made of?

Stratified Squamous Epithelium

What are Keratinocytes?

They produce keratin

What is keratin?

the fibrous protein that makes the epidermis a tough protective layer

Langerhans cells

Langerhans cells are members of the *dendritic cell* family. Their main role is to alert other components of the adaptive immune system to the presence of pathogens and other infectious agents on the skin.

What are cornified epidermis cells?

the upper layer composed of mostly dead, differentiated cells (stratum corneum) with a lot of keratin which helps the skin maintain some protection against water loss and bacteria. Prevents skin from sloughing off

Melanocytes

Melanin pigment (dark brown-black), protects DNA. Freckles, Albinism, Vitiligo

Nails

strengthen & protect finger tips when grasping, used for scratching

Mucous Epithelium

same as skin but w/o cornified layer, hair, sweat glands. Moisture and mucus prevent desiccation.

where are Mucous Epithelium cells found

Conjunctiva, Vagina, Mouth-Pharynx-Oesophagus

Dermis

Middle layer of skin

The dermis layer contains _____________

Sweat Glands, Hair follicles, Neuroreceptors, Capillary beds (heat control)

dermal papillae

Found in the upper layers of the dermis, they create your fingerprint pattern for grip

What is the purpose of hair?

protects bony ridges, sense of touch

Arrector Pili

a smooth muscle attached to hair follicles that causes "goose bumps" to appear on the skin when contracted

What do sweat glands do?

They secrete sweat, located in the dermal layer of the skin. This helps regulate body temperature

Eccrine glands

glands that produce sweat; found over most of the body. whole body, #palms, soles, axilla (armpit)

Apocrine glands

produce sweat (puberty) axilla, pubic area, areola. Sexual (?)

Sebaceous glands

secrete sebum (oil) into the hair follicles where the hair shafts pass through the dermis

Hypodermis

connecting the dermis layer of your skin to your muscles and bones, and contains fat to insulate your body and protect your body from harm

Symptoms of aging skin

skin thinner (feel cold), less elastic, drier/itching, wounds easily, skin cancers more common (probably due to sun burns or exposure to toxic agents earlier in life.)

FRICTION causes

calluses, corns

WOUNDS cause

scars, keloids

First Degree burn

Epidermis only. Inflammation only (redness and pain)

Second Degree burn

Dermis. Inflammation + blisters

Third Degree burn

Hypodermis and deeper. Skin charred, painless

WART

virus

MELANOMA

melanocyte cancer

ALOPECIA

hair loss

NEVUS

mole

URTICARIA

hives/ rashes

PRURITIS

itching

DECUBITUS ULCERS

bed sores

Central Nervous System (CNS)

Brain and Spinal Cord

Peripheral Nervous System (PNS)

Cranial and Spinal Nerves branching out from cns

Sensory Division

picks up stimuli, returns info to CNS through afferent nerves

Motor Division

sends directions from your brain to your muscles and glands

Somatic Nervous System (SMS):

part of PNS, controls skeletal muscles movement

Autonomic Nervous System (ANS)

part of PNS. to viscera, smooth Mm, glands, etc. keeps your heart beating, lungs breathing, and stomach churning

sympathetic system

part of ANS (of PNS). controls “fight-or-flight” responses. In other words, this system prepares the body for strenuous physical activity.

parasympathetic system

part of ANS (of PNS). a set of nerves that helps the body return to a normal resting state

Neuroglia \[CNS\]

cells that support and protect neurons

Astrocytes

connective tissue of CNS. form blood brain barrier by anchoring neurons to blood supply

What is the role of the blood brain barrier

shields the brain from toxic substances in the blood, supplies brain tissues with nutrients, and filters harmful compounds from the brain back to the bloodstream.

Oligodendrocytes 

form myelin sheaths of axons in CNS. Insulates-protects-heals. can connect to Many Axons or places on Axon

Microglia

Act as phagocytes in CNS, eating damaged cells and bacteria, act as the brains immune system

Ependyma

membrane lining the central canal of the spinal cord and the ventricles of the brain. Move Cerebrospinal Fluid (CSF) in chambers and passages inside CNS; ciliated

Gliomas

Brain tumors that grow rapidly and are highly malignant; blood-brain barrier decreases effectiveness of chemotherapy; treatment consists of radiation or surgery

Neurons \[CNS & PNS\]

Individual cells in the nervous system that receive, integrate, and transmit information.

Cell Body of neurons

Contains nucleus, unmyelinated, Nissl Bodies (Rough ER with colour)

Dendrites

Fibre(s) attached to cell body of neurons, bring info to cell body

Axon

the extension of a neuron, ending in branching terminal fibers, through which messages pass to other neurons or to muscles or glands

Axon Hillock

trigger zone of neuron; the conical projection that connects the cell body to the axon

Neurofilaments

Fine thread-like structures that form a matrix in the cytoplasm; they provide support/strength for the cell membrane and maintain the shape of the neuron.

Collateral Branches

side branches of axons allow single neuron to communicate with several other cells

Axon Terminal

The endpoint of a neuron where neurotransmitters are stored, Synaptic Bulbs

Synapse

Approximation of one axon with the cell body or dendrite of another neuron; gap. Neurotransmitters are released and cross thru fluid gap to receptors on target neuron

Neurogenesis

creation of new neurons in the adult brain. There’s no mitotic apparatus, hence no mitosis, death. However, new neurons can replace

Unipolar Neurons

sensory. have a short single process leaving the cell body. afferent neurons

Bipolar Neurons

special senses. A neuron that has only two projections (one axon/one dendrite) from the cell body. found in retina of eye

Multipolar

motor. single axon with many dendrites. most common neurons and vary greatly in shape.

Schwann Cells \[PNS\]

Similar to Oligodendrites by wrapping axons w/myelin, but 1 Schwann to 1 Axon (1:1); Supporting cells of the peripheral nervous system responsible for the formation of myelin.

Myelin Sheaths

Lipid electrically insulates axon, protects and heals.

Nodes of Ranvier

Gaps between Schwann cells (and Oligodentrites); not insulated. Electrical impulses in both PNS and CNS leap from node to node down axon. Hence, heavily \n myelinated nerves (e.g. joint information) carry impulses much faster than unmyelinated \n nerves (e.g. Pain, Touch).

Grey Matter

The portions of the central nervous system that are abundant in cell bodies of neurons rather than axons. Unmyelinated.  While the grey matter is mainly located on the surface of the brain. The spinal cord is arranged in the opposite way, with grey matter found deep inside its core

grey matter nucleus

clusters of cell bodies inside the CNS for common function

Nerve and Muscle tissue are excitatory meaning ____

a voltage is created across their membranes

What is the role of the Na+/K+ Pump

Active transporter that moves three Na+ out of a cell and two K+ into the cell against their respective concentration gradients.

What does it mean for a neuron to be polarized?

Disequilibrium of these electrolytes (Na+/K+) across membrane. Creates a Membrane Potential (voltage); An axon membrane at rest where the inside of the cell is negative compared with the outside of the cell

Membrane Potential

\- The voltage across a cell's plasma membrane.

\- maintained by sodium-potassium pump and leak channels

Resting Membrane Potential:

\-70 mv

Threshold Potential:

\-55 mv, once this is reached Na+/K+ gates open

Action Potential:

\+30 mv, a wave of electricity sweeping down axon from Na+/K+ gate to gate like ring of fire

Depolarization

Describes nerve firing, i.e. creating Action Potential; The process during the action potential when sodium is rushing into the cell causing the interior to become more positive.

At what rate do cells depolarize?

Nerve depolarises rapidly = Nerve fires = like electrical spark.

Na+/K+ gates open when

threshold is crossed

What causes the polarised membrane to “depolarise”

Na+ and K+ rushing into and out of \n cell

Hyperpolarizing

increasing the polarity of a neuron, making it less likely to fire

Hypopolarizing

 the initial increase of the membrane potential to the value of the threshold potential. The threshold potential opens voltage-gated sodium channels and causes a large influx of sodium ions

Lidocaine

common local anesthetic: Blocks Na/K gates of nerve fibres → no Impulse.

All or None Principle

As with muscle. No impulse will occur until membrane potential reaches threshold. Then, a full action potential is produced—never more or less.

If cell body is damaged_____

the neuron will most likely die and cannot be replaced

If myelin sheath is damaged

the axon *may* die from that point to the terminal

If myelin sheath is damaged in the PNS AND the axon damage is not extensive,

it may repair or even regrow to the terminal (Incredibly slow) because Schwann cells can reproduce and insulate the axon’s healing

If myelin sheath is damaged in the CNS the axon will _______

not heal because Oligodendrites do not reproduce and insulate

Blocking the release of neurotransmitters into the synaptic cleft

decreased response

Blocking attachment of neurotransmitters to target tissue receptors

decreased response

Blocking removal of neurotransmitters from the synaptic cleft.

increased response

Inhibiting neurotransmitter receptors by hyperpolarizing them.

decreased response

Exciting neurotransmitter receptors by hypopolarizing them.

increased response

grey matter

The portions of the central nervous system that are abundant in cell bodies of neurons rather than axons. Unmyelinated.

grey matter Nucleus

clusters of cell bodies inside the CNS for common function

grey matter Ganglion

clusters of cell bodies outside the CNS for common function

White Matter

Whitish nervous tissue of the CNS consisting of neurons and their myelin sheaths.