Intro to Physiology of Exercise Exam 2

Functions of the skin

• protection

• temperature regulation

• sensory perception

• synthesis of vitamin D

• excretion

• absorption

Layer of the skin (deep-superficial)

• subcutaneous tissue

• dermis

• epidermis

Epidermis

• thinnest, outer layer

• composed of epithelium

Dermis

• thicker, inner layer

• composed of connective tissue

Subcutaneous tissue

• located beneath the dermis

• it is not considered part of the skin but has very close proximity to the skin

Functions of epidermis

• stratified squamous epithelium

• avascular

• high cell turnover

• keratinized

• protection

Cells in epidermis

• keratinocytes

• melanocytes

• dendritic cells

• tactile (Merkel) cells

Keratinocytes

Produces tough fibrous protein that waterproofs the skin and protects against abrasion

Melanocytes

Produce brown-black pigment

Dendritic cells

• derived from monocytes (type of white blood cells)

• remove pathogen and alert the system of threat

Tactile (Merkel) cells

Sensory input

Composition of epidermis (deep-superficial)

• stratum basale

• stratum spinosum

• stratum granulosum

• stratum luciderm

• stratum corneum

Stratum basale

Innermost layer, cell division

Stratum spinosum

Keratinocytes produce keratin, adds strength

Stratum granulosum

Cells contain granules, cells go through apoptosis (programmed cell death)

Stratum luciderm

Only in thick skin and appears lucid (transparent), adds extra protection

Stratum corneum

20-40 layers of dead keratinized cells, protective barrier

Structure of dermis

• dense connective tissue

• collagen and elastic fibers

Components of dermis

• blood vessels

• nerves

• sweat glands

• sebaceous glands

• hair follicles

• sensory receptors

Structure of hypodermis

• loose connective tissue and adipose tissue

• fat storage

• absorbs shock forces

• insulates the body

Compare and contrast thick skin to thin skin

• Thick skin: palms of hand/soles of feet, no hair follicles/has stratum lucidum

• Thin skin: covers most of the body, contains hair follicles and sebaceous glands/no stratum lucidum

Accessory structures

• sweat glands: eccrine & apocrine

• oil glands: sebaceous glands

• hair

• nails

• sensory receptors

• skin color

• temporary changes in skin color

Sweat glands: Eccrine glands

• thermoregulation

• produce watery sweat

• activated during exercise

Sweat glands: Apocrine glands

• activated during stress or emotional response

• produces a thicker secretion

• causes body odor

Oil glands: Sebaceous glands

• associated with a hair follicle

• secrete sebum into follicle

• lubricates hair and skin

• antimicrobial properties

Hair

• composed of keratinized epidermal cells formed at base of the hair follicle

• consists of hair shaft, hair root, hair follicle

• associated structures: arrector pili muscle, sebaceous glands, sensory nerve endings

Nails

• composed of hard keratin

• parts of the nail include nail body, nail root, nail matrix, lunula, cuticle

• protection (distal surface of fingers/toes

• helps with manipulation

Sensory receptors

• haor root plexus

• mechanoreceptors

• thermoreceptors

• nociceptors

Skin color

• determined by a combination of pigments, blood flow, and underlying tissue composition

• 3 pigments in the skin: melanin, carotene, hemoglobin

Erythema

• redness due to increased blood flow

• common during exercise or inflammation

Pallor

• pale appearance from reduced blood flow

• seen in shock, cold exposure, or dehydration

Cyanosis

• bluish discoloration due to poor oxygen

• medical concern

Jaundice

• yellowing due to bilirubin buildup

• sign of liver dysfunction

Thermoregulation

If body temperature increases:

• radiation

• conduction

• convection

• evaporation

If body temperature decreases:

• involuntary muscle contractions (shivering)

• blood vesicles constrict

During exercise how does the body maintain a stable body temperature?

1. during exercise muscle contracts and produces heat which causes the body’s core temperature to rise

2. cooling mechanisms cause vasodilation which activates your body to sweat

3. body temperature returns to normal

• takes place mainly in the hypodermis nut can take place in dermis

Skeletal muscle

• striations

• many nuclei/cell

• long/parallel shaped cells

• voluntary

• attached to bones, dermis, ligaments, and other muscles

Smooth muscle

• no striations

• one nucleus/cell

• short and tapered cells

• involuntary

• visceral organs, blood and lymphatic vessels, and skin

Cardiac muscle

• striations

• one nucleus/cell

• short and branching cells

• involuntary

• heart

Hierarchy of muscle structure (largest to smallest)

Muscle → muscle fascicle → muscle fiber (cell) → myofibril → myofilament

Muscle fiber (cell) is surrounded by:

Sarcolemma

2 types of myofilaments

• actin

• myosin

Sarcolemma

Plasma membrane of a muscle fiber maintaining the integrity of the cell

Sarcoplasm

Cytoplasm of a muscle fiber that contains organelles

Nuclei

Contain DNA, which determines cell structure and function

Sarcoplasmic reticulum

Smooth ER in a muscle fiber that stores calcium

Transverse tubules

Extensions of the sarcolemma that penetrate into the sarcoplasm carrying electrical impulses, which trigger the release of the calcium from the sarcoplasmic reticulum

Myofibril

A bundle of myofilaments

Myofilaments

Threadlike contractile proteins that interact to produce contractions

Sarcomere

Contractile unit of the muscle fiber

Sarcomere (z line)

End of sarcomere, actin is attached on both sides

Sarcomere (I band)

Only actin

Sarcomere (A band)

Spans the length of myosin (doesn’t change length)

Sarcomere (H band)

Only myosin

Sarcomere (M line)

Center line of sarcomere (doesn’t move)

Actin

• 2 strands arranged in a double helix

• troponin

• tropomyosin

• thin filament

Myosin

• globular heads with a hinge point and fibrous tail

• thick filament

• moves like a windshield wiper

Motor unit

• large motor units: strength

• small motor units: precision

Action potential

Electrical stimulation

Neuromuscular junction

The place where a motor neuron meets a muscle fiber and sends a signal to make the muscle contract

Synaptic cleft

The tiny gap between the nerve cell and the muscle cell at the neuromuscular junction

Acetylcholine (ACh)

A neurotransmitter (chemical messenger) that carries the signal from the nerve to the muscle to start contraction

Sliding filament model

The theory that muscles contract because actin and myosin filaments slide past each other, shortening the muscle

All or nothing principle

A muscle fiber either contracts completely or not at all when stimulated — there is no partial contraction of a single fiber

Phases of muscle contraction

• latent phase: the short delay between the stimulus and the start of contraction

• contraction phase: the muscle shortens and generates force

• relaxation phase: the muscle returns to its resting length

Origin

The attachment point of a muscle that stays relatively still during movement

Insertion

The attachment point of a muscle that moves during contraction

Agonist

The main muscle responsible for a movement (prime mover)

Antagonist

The muscle that opposes or reverses the movement of the agonist

Isotonic

A contraction where the muscle changes length and movement occurs.

• Concentric = muscle shortens

• Eccentric = muscle lengthens

Isometric

A contraction where the muscle produces force but does not change length (no movement)

Flexion

Decrease in the angle of the bones forming the joint

Extension

Increase in the angle of the bones forming the joint

Hyperextension

Increase in the angle of the bones forming the joint beyond the anatomical position

Dorsiflexion

Flexion of the foot at the ankle

Plantar flexion

Extension of the foot at the ankle

Abduction

Movement of a bone away from the midline

Adduction

Movement of a bone toward the midline

Rotation

Movement of a bone around its longitudinal axis

Medial rotation

Rotation of a limb so its anterior surface turns medially

Lateral rotation

Rotation of a limb so its anterior surface turns laterally

Circumduction

Movement of the distal end of a bond in a circle while the proximal end forms the pivot joint

Eversion

Movement of the sole of the foot laterally

Inversion

Movement of the sole of the foot medially

Pronation

Rotation of the forearm when the palm is turned inferiorly or posteriorly

Supination

Rotation of the forearm when the palm is turned superiorly or anteriorly

Protraction

Movement of the body part posteriorly

Retraction

Movement of the body part anteriorly

Elevation

Movement of a body part superiorly

Depression

Movement of a body part inferiorly

Opposition

Movement of the thumb to touch the other 4 fingers

Reposition

Movement of the thumb back to the anatomical position

Epicranius frontalis

Epicranius frontalis

• Origin: Epicranial aponeurosis

• Insertion: Skin and muscles above the eye

• Action: Raises eyebrow and wrinkle forehead horizontally

Orbicularis oculi

• Origin: frontal bone and maxilla

• Insertion: skin around the eye

• Action: closes eye

Orbicularis oculi

Orbicularis oris

• Origin: muscles around the mouth

• Insertion: skin around the lips

• Action: closes and puckers lips; shapes lips during speech

Orbicularis oris

Masseter

• Origin: Zygomatic arch

• Insertion: Lateral surface of mandible

• Action: Raises mandible

Masseter

Temporalis

• Origin: Temporal bone

• Insertion: Coronoid process of mandible

• Action: Raises mandible