Muscle Physiology Quiz

Anatomy and Physiology I - The Muscular System

• Muscle is one of the four basic tissues in the body, composed of cells that can shorten and lengthen.
• Muscles carry out commands from the nervous system (except cardiac and smooth muscle).
• Three types of muscle:
  • Skeletal muscle: voluntary, moves the skeleton, striated, somatic nervous system.
  • Cardiac muscle: involuntary, only found in the heart, striated, autonomic nervous system.
  • Smooth muscle: involuntary, found throughout the body (e.g., eyes, lungs, stomach, intestines, bladder, reproductive tract), non-striated, autonomic nervous system.
• Myo- refers to muscle (e.g., myositis is muscle inflammation).
• Sarco- refers to muscle cells (e.g., sarcoplasm is the cytoplasm of a muscle cell).
• Skeletal muscle can be controlled consciously, but also has an "automatic" feature to control/regulate functions like breathing.
• Gross anatomy:
  • Belly: thick, central, contractile portion of the muscle.
  • Tendons: fibrous bands connecting muscle to bone.
  • Aponeuroses: broad fibrous bands connecting muscles to bone or other muscles.
  • Linea alba: white line running lengthwise between abdominal muscles on the ventral midline.

Anatomy and Physiology I - Muscle Action

• Movement is caused by pulling on attachment points.
• Prime movers (agonists): muscles primarily responsible for movement.
• Antagonists: muscles that oppose the prime mover to control movement.
• Synergists: muscles that assist the prime mover in a specific action.
• Fixators: muscles that stabilize joints to allow other movements to occur.

Anatomy and Physiology I - Muscle Names

• Muscles names may be based on several factors, e.g., shape, location, direction of fibers, number of heads, or attachment sites.

Anatomy and Physiology I - Microscopic Anatomy

• Skeletal muscle cells (fibers) are long, cylindrical, and multinucleated.
• Myofibrils are composed of contractile proteins (actin and myosin).
• Myofibrils are made up of sarcomeres (repeating units)
• Sarcomeres are the basic contractile units that cause shortening of the muscle.
• The parts of the sarcomere include: I band, Z band, A band
• These components work together to create the contraction in skeletal muscles.

Anatomy and Physiology I - Connective Tissue

• Endomysium: surrounds individual muscle fibers.
• Perimysium: surrounds groups of muscle fibers (fascicles).
• Epimysium: surrounds the entire muscle.
• These connective tissues help hold the muscle together during contraction.

Anatomy and Physiology I - Neuromuscular Junction

• The site where the ends of motor nerve fibers connect to muscle fibers.
• Neurotransmitters initiate the process of muscle contraction.
• Acetylcholine is the neurotransmitter used to initiate the contraction of skeletal muscle, it is quickly broken down by acetylcholinesterase.
• The impulses from motor nerve fibers travel through the T tubules and cause released Ca2+ ions to initiate contraction.

Anatomy and Physiology I - Mechanics of Contraction

• During a relaxed phase, actin/myosin slightly overlap.
• Myosin filaments ratchet back to contract and pull actin filaments towards the center of the myosin filament, shortening the sarcomere

Anatomy and Physiology I - Chemistry of Muscle Contraction

• ATP is used to provide energy for muscle contraction.
• Creatine Phosphate (CP) acts as a backup energy source.

Anatomy and Physiology I - Muscle Contraction Phases

• Latent phase: brief delay between stimulus and contraction.
• Contraction phase: muscle shortens in response to stimulus.
• Relaxation phase: muscle returns to resting length.

Anatomy and Physiology I - Muscle Memory

• Muscle memory is the nervous system training to improve the synchronization of muscle contractions.

### Anatomy and Physiology I - Cardiac Muscle

• Cardiac muscle cells are smaller than skeletal muscle cells and have one nucleus per cell.
• Intercalated discs: connect cells and allow for coordinated contraction.
• No external stimuli needed for contraction, but the rate is determined by the fastest cell.
• Impulses spread from cell to cell, coordinated by conduction system (starts in the sinoatrial (SA) node).
• Sympathetic nerves speed up/strengthen and parasympathetic nerves slow down contraction.

Anatomy and Physiology I - Smooth Muscle

• Found in sheets or groups, non-striated, involuntary.
• Cells have fusiform (spindle-shaped) structure, with one nucleus.
• Actin and myosin filaments arranged diagonally, giving a non-striated appearance.
• Cells can contract in response to stretch (visceral muscle) or specific nerve signals (multiunit smooth muscle).
• No need for external stimulation for contraction(ex. visceral smooth muscles in the gut).
• Sympathetic nervous decreases and parasympathetic increases activity.

Anatomy and Physiology I - Integument (Skin)

• Outer covering of the body, composed of four types of tissue.
• Epidermis and dermis are the major layers.
• Epidermis: outermost layer (keratinized stratified squamous epithelium).
• Keratinocytes: predominant cell type.
• Melanocytes: produce melanin (pigment).
• Langerhans cells: immune function.
• Merkel cells: touch sensation.
• Dermis: underlying layer (fibrous connective tissue).
• Hypodermis/subcutaneous layer: deep connective tissue layer, adipose tissue for insulation.
• Sweat glands (apocrine and eccrine): regulate body temperature.
• Sebaceous glands: secrete sebum (oils) to lubricate hair and skin
• Hair follicles (hair shaft, bulb): structure for hair growth, nerve endings for sensory input to the skin.

Anatomy and Physiology I - Hair

• Hair is crucial in maintaining temperature, sensory input.
• Divided into three types of hairs (depending on the function and sensitivity).
  • Guard hairs: primary (longer, straighter, thicker)
  • Secondary hairs: shorter, softer (wavy, bristled).
  • Tactile hairs: (whisker hairs), are specialized for touch and sensory input.

Anatomy and Physiology I - Sebaceous Glands

• Found in most body areas, except palms of hands/soles of feet.
• Secrete sebum (oil), lubricating hair and skin.
• Prevents skin drying, plays a role in skin's waterproofing, antimicrobial action.

Anatomy and Physiology I - Sweat Glands

• Eccrine sweat glands: most numerous, regulate body temperature.
• Apocrine sweat glands: concentrated in axillae, pubic region, and areola; their function and secretions are often associated with sexual development.

Anatomy and Physiology I - Nasolabial Planum

• Also known as the nasal planum.
• Composed exclusively of the three epidermal layers.
• This is a specialized structure primarily found in sheep, cattle and goats.

Anatomy and Physiology I - Anal Glands

• Musk/scent glands located near the anus.
• Act as a reservoir for secretions.
• Primarily released during defecation/fear.
• May be affected with infections.