Unit 2 notes

Phototransduction

The process by which light is converted into electrical signals in the retina.

Accommodation

The adjustment made by the eye to focus on near objects, involving changes in lens shape and pupil constriction.

Convergence

The medial rotation of eyeballs causing the eyes to converge towards the object being viewed.

Retina

The light-sensitive layer at the back of the eye that contains photoreceptor cells (rods and cones) responsible for capturing light.

Rods

Photoreceptor cells in the retina specialized for dim light and peripheral vision, more sensitive to light but do not provide color vision.

Cones

Photoreceptor cells in the retina specialized for bright light and color vision, concentrated in the central region of the retina.

Photoreceptors

Cells in the retina that are sensitive to light and responsible for initiating the process of vision.

Rhodopsin

A light-sensitive receptor protein in the rods of the retina that plays a key role in the phototransduction process.

Bipolar cells

Neurons in the retina that receive signals from photoreceptor cells and transmit them to ganglion cells.

Ganglion cells

Neurons in the retina that generate action potentials and transmit visual information to the brain via the optic nerve.

Muscle Tissue

Tissue that makes up nearly half of the body's mass, responsible for transforming chemical energy (ATP) into mechanical energy to exert force.

Skeletal Muscle

Muscle tissue attached to bones and skin, composed of elongated cells called muscle fibers, striated in appearance, and under voluntary control.

Cardiac Muscle

Muscle found only in the heart, striated, capable of contracting without nervous system stimulation, and under involuntary control.

Smooth Muscle

Muscle found in the walls of hollow organs, not striated, can contract without nervous system stimulation, and under involuntary control.

Epimysium

Connective tissue surrounding the entire skeletal muscle.

Perimysium

Fibrous connective tissue surrounding fascicles (groups of muscle fibers).

Endomysium

Connective tissue surrounding each muscle fiber.

Motor Unit

Functional unit consisting of a motor neuron and the muscle fibers it controls, allowing for fine control of muscle movement.

Sarcomere

The smallest contractile unit of a muscle fiber, composed of thick and thin myofilaments made of contractile proteins.

T Tubule

Continuations of the sarcolemma that help transmit action potentials deep into the muscle fiber.

Sarcoplasmic Reticulum (SR)

Smooth endoplasmic reticulum network surrounding each myofibril, involved in regulating intracellular calcium levels.

Troponin-Tropomyosin Complex

Regulatory proteins associated with actin that control the interaction between myosin and actin during muscle contraction.

Neuromuscular Junction (NMJ)

The point of contact between a motor neuron and a skeletal muscle fiber, essential for muscle contraction.

Action Potential

Electrical signal that triggers muscle fiber contraction, initiated by changes in electrical charges in the sarcolemma.

Excitation-Contraction (E-C) Coupling

Events that link the action potential on the sarcolemma to the sliding of myofilaments, leading to muscle contraction.

Sliding Filament Model

Mechanism of muscle contraction where thin filaments slide past thick filaments, causing actin and myosin to overlap and generate force.

Cross Bridge Cycle

Series of events involving the attachment, pivoting, detachment, and re-energizing of myosin heads to actin filaments during muscle contraction.

Myosin

A protein involved in muscle contraction that binds to actin and requires ATP for detachment.

Actin

A protein that interacts with myosin during muscle contraction.

ATP

Adenosine triphosphate, a molecule that provides energy for cellular processes, including muscle contraction.

Muscle Contraction

The process by which muscle fibers generate tension and shorten in length.

Motor Unit

A motor neuron and all the muscle fibers it innervates, responsible for muscle contractions.

Contraction Types

Concentric contraction (shortening), eccentric contraction (lengthening), and isometric contraction (no change in length).

Skeletal Muscle

Voluntary muscle tissue attached to bones, characterized by striations.

Smooth Muscle

Involuntary muscle tissue found in the walls of internal organs, lacking striations.

Cardiac Muscle

Involuntary muscle tissue found only in the heart, characterized by striations.

Osteocytes

Bone cells that act as stress sensors and communicate with other bone cells for repair and remodeling.

Osteoblasts

Cells responsible for bone formation by secreting the organic components of the bone matrix.

Parathyroid hormone (PTH)

Hormone that stimulates osteoblasts to secrete factors important for osteoclast formation.

Osteocytes

Cells that make up 90% of all bone cells, derived from osteoblasts, and function as mechanosensing cells within the bone network.

Osteoclasts

Multinucleated cells derived from mononuclear monocyte-macrophage cells responsible for bone resorption.

Bone Extracellular Matrix

Comprises the inorganic (mineral) and organic matrices, providing bone strength and flexibility.

Bone Remodeling

Physiological process involving the removal of old bone by osteoclasts and formation of new bone by osteoblasts to maintain bone mass and quality.

Endochondral Ossification

Process of bone formation from a cartilage model, more common than intramembranous ossification.

Red Bone Marrow

Site of red blood cell production, transitioning to yellow bone marrow with age which stores fat.

Compact Bone

Type of bone tissue characterized by osteons made up of concentric circles called lamellae.

Countercurrent Mechanism

Mechanism where water and blood flow in opposite directions, maximizing gas exchange efficiency along respiratory surfaces.

Inhalation

The process of breathing in, where the respiratory muscles contract, increasing the thoracic cavity volume, causing the lungs to expand and air to move in.

Exhalation

The process of breathing out, where the respiratory muscles relax, decreasing the thoracic cavity volume, causing the lungs to shrink and air to move out.

External Respiration

The exchange of gases (oxygen and carbon dioxide) between the lungs and the blood in the pulmonary capillaries.

Internal Respiration

The exchange of gases (oxygen and carbon dioxide) between the blood in systemic capillaries and the body tissues.

Hemoglobin

The protein in red blood cells that carries oxygen, with most oxygen (98.5%) bound to it.

Bohr Effect

Describes how CO2 levels and blood pH affect hemoglobin's affinity for oxygen, leading to shifts in the O2-Hb dissociation curve.

O2-Hb Dissociation Curve

Illustrates the relationship between hemoglobin saturation with oxygen and the partial pressure of oxygen in the blood.

Medulla Oblongata

The part of the brain where the control center for regulating respiratory rate is located.

Respiratory Depression

A condition where the respiratory rate decreases, often associated with opioid use, and can be countered by drugs like Doxapram.

Neuromuscular Junction

The connection between a motor neuron and a muscle fiber where acetylcholine binding leads to muscle fiber depolarization.

Myasthenia gravis

An autoimmune disorder where antibodies target and block nicotinic acetylcholine receptors at the neuromuscular junction, leading to impaired neuromuscular transmission and muscle weakness.

Neuromuscular junction (NMJ)

The site where a motor neuron forms a synapse with a muscle fiber, crucial for the transmission of nerve impulses to initiate muscle contraction.

Acetylcholine (ACh)

A neurotransmitter released at the neuromuscular junction to stimulate muscle contraction.