Lec 1 - Mam Phys

What is physiology?

The study of the functions of all parts of the body and how organ systems work together to sustain life.

What is the primary goal of physiology?

To understand how organ systems interact to maintain homeostasis.

What is homeostasis?

The maintenance of a relatively constant internal environment despite changing internal or external conditions.

What is the central organizing principle of physiology?

Homeostasis.

What is a homeostatic imbalance?

A disturbance of the body's normal internal conditions caused by a stimulus.

What is a stimulus?

Any change in the internal or external environment that disrupts homeostasis.

What is an open-loop control system?

A control system in which the output has no effect on future control actions.

Does an open-loop control system use feedback?

No.

What is the pathway of an open-loop control system?

Control center → Effector → Controlled variable.

Give an example of an open-loop control system.

Blinking when an object approaches the eye.

Why is blinking considered an open-loop system?

The eyelid closes regardless of whether the response changes the original stimulus.

What is a closed-loop control system?

A feedback system in which the output influences future control actions.

What is the pathway of a closed-loop control system?

Control center (set point) → Effector → Controlled variable → Sensor → Control center.

What determines the control action in a closed-loop system?

The output of the system.

What are the two types of feedback systems?

Negative feedback and positive feedback.

What is negative feedback?

A feedback mechanism that reverses or reduces the original stimulus.

What is the purpose of negative feedback?

To restore homeostasis.

Is negative or positive feedback more common in physiology?

Negative feedback.

What is positive feedback?

A feedback mechanism that amplifies the original stimulus.

Does positive feedback restore homeostasis?

No; it moves the system farther from the set point until a specific event ends the cycle.

What happens during hemorrhage that activates negative feedback?

Blood pressure decreases.

How does the body compensate for decreased blood pressure during hemorrhage?

By increasing fluid reabsorption, vasoconstriction, renal fluid conservation, and vasoconstrictor release.

Name one endogenous vasoconstrictor released during hemorrhage.

Angiotensin II.

Name another endogenous vasoconstrictor released during hemorrhage.

Arginine vasopressin (ADH).

Name another endogenous vasoconstrictor released during hemorrhage.

Catecholamines.

What is the overall goal of the body's response to hemorrhage?

To increase blood pressure back toward normal.

What is a receptor in a control system?

A structure that detects a stimulus.

What is the role of a sensory neuron in an open-loop control pathway?

It carries information from the receptor to the spinal cord.

What is the role of an interneuron?

It relays information from the sensory neuron to the motor neuron.

What is the role of a motor neuron?

It carries commands from the CNS to an effector.

What is an effector?

A muscle or gland that produces the response.

What is pathophysiology?

The study of disease caused by failure to maintain homeostasis.

What is the underlying cause of most diseases according to physiology?

The inability to maintain homeostasis.

How can negative feedback fail?

It becomes overwhelmed.

What may happen when negative feedback fails?

Positive feedback mechanisms become destructive.

How can aging contribute to disease?

Bodily control systems become less efficient.

How can genetics contribute to homeostatic imbalance?

Genetic mutations may disrupt normal physiological processes.

How can pathogens disrupt homeostasis?

By overwhelming the body through infection.

How can environmental factors disrupt homeostasis?

Through toxins or other harmful exposures.

How many organ systems are in the human body?

11.

Which organ systems are most directly responsible for maintaining homeostasis?

The nervous system and the endocrine system.

Why is the nervous system important for homeostasis?

It provides rapid control and communication between organs.

Why is the endocrine system important for homeostasis?

It provides slower, longer-lasting hormonal regulation.

Which system generally responds first to a disturbance in homeostasis?

The nervous system.

Which system produces long-lasting responses?

The endocrine system.

What is interstitial fluid?

The fluid surrounding cells within tissues.

Why is interstitial fluid important?

It serves as the immediate environment for cells and facilitates exchange of nutrients and wastes.

Name the 11 organ systems.

Integumentary, skeletal, muscular, nervous, endocrine, cardiovascular, lymphatic, respiratory, digestive, urinary, reproductive.

Which organ system provides rapid electrical communication?

Nervous system.

Which organ system communicates through hormones?

Endocrine system.

Why must cells, tissues, organs, and organ systems communicate?

To maintain homeostasis.