Lecture 1, Intro to Physiology

Question 1

Anatomy

Answer 1

the study of the physical structure and shape of the body and its components
- gross anatomy: the study of large bodily structures (often whole organ systems)
- microscopic anatomy: the study of smaller bodily structures (often at the cell)

Question 2

Physiology

Answer 2

the study of how living organisms function
- investigations of the mechanisms by which the body can do what it can do
- how parts of the body work together at various levels of organization
pathophysiology: a sub-field of physiology that focuses of disease states

Question 3

Levels of Physiology

Answer 3

a. cellular physiology - the study of function at the cellular level
b. systemic physiology - the study of function of whole organ systems
c. pathology physiology (pathophysiology) - the study of disease states, the effects of pathology on cells, organs, organ systems or the whole organism

Question 4

Homeostasis

Answer 4

definition: the dynamic process of maintaining a stable (not constant, just in a normal range) internal environment)
- homeostatic control systems are mechanism that respond to any change in the internal environment that requires a reaction to correct the change and maintain physiological variable within normal ranges (internal environment)
- the internal environment of the body is dynamic, not static; small adjustments are continually made to allow for the body to meet new demand; adjust to new stressors (does not stay constant)

Question 5

Dynamic constancy - homeostasis

Answer 5

a given variable that can fluctuate in the body in the short term, but will be predictable and stable in the long term

Question 6

Steady state

Answer 6

a state in which a variable in a system is not changing, but energy must be continuously added to maintain a stable, homeostatic environment
- different from equilibrium, which is a state where the variable does not require any input of energy to maintain constancy

Question 7

Reflex arc

Answer 7

reflex: a specific, voluntary, built-in response to a particular stimulus
- may or may not involve conscious awareness
- ex. when your hand immediately withdraws after touching a hot stove
reflex arc: the pathway mediating a reflex
- the stimulus refers to a detectable change in the internal or external environment
- the change is detected by a receptor
- the receptor sends a signal to the integrating center along the afferent pathway
- the integrating center processes the signal and evokes a response
- a signal is sent to an effector along the efferent pathway
- afferent means to the brain
- efferent means away from the nervous system
* the response resulting from a reflex does not necessarily always the stimulus

Question 8

Feedback System

Answer 8

• feedback system responds to a change after it has occurred, as it requires the change to be sensed and relayed back to a control center, prior to the reaction or response
  steps: a variable fluctuates from a set point -> the change is sensed and relayed back to appropriate control center -> a response is elicited -> the variable returns back to normal (negative feedback) OR the variable is further perturbed from the baseline (positive feedback)
  *sensor, control center and receptor for a feedback system

Question 9

Positive feedback VS. Negative feedback

Answer 9

positive: accelerates a process by moving a variable further away from a set point
negative: minimize change from the set point of a system, leading to stability

Question 10

Feedforward System

Answer 10

feedforward systems anticipate a change that is about to happen and elicit a response before it happens
- a change in the variable in anticipated, and a response is evoked to minimize the fluctuations in the variable (does it beforehand, the change will happen to a lesser degree)
steps: change in the variable is anticipated -> a response a elicited -> the variable fluctuates from that set point, but to a lesser degree due to the response
* do not need a sensor for feedforward system
* in some cases, homeostatic control systems include both feedforward and feedback mechanisms
* there are also cases where the set point of a variable may be temporarily reset, such as body temperature during a fever, or blood pressure during exercise

Question 11

General Principals for Physiology

Answer 11

1. Homeostasis is essential for health and survival – there is a necessity to maintain physiological variables within normal ranges
   ◦ Challenges to homeostasis may result from disease, or exposure to chronic/extreme stressors
   ◦ Have a narrow range where the body functioning is ideal, or else it will decline
2. Organ systems’ functions are coordinated with each other
   ◦ Organ system do not function independently, but instead are highly integrative with one another
   ◦ Organs do not function in isolation
3. Most physiological functions are controlled by multiple regulatory systems, often working in opposition
   ◦ Feedforward and feedback control mechanisms
   ◦ Can have many types of loops, can help to have more than one to get control of the variable
4. Information flow between cells/tissues/organs is an essential feature of homeostasis, and allows for integration of physiological processes (designed and optimized to not waste energy)
5. Exchange of materials between compartments and across membranes occurs in a controlled manner (may get wasted energy if it is not controlled)
   ◦ Compartmentalization is an important feature in physiology
6. Physiological processes are dictated by the laws of physics and chemistry
7. Physiological processes require the transfer and balance of matter and energy
8. Structure is a determinant of (and has coevolved with) function (structure dictates function - important)

Question 12

The Heirarchy of Body Organization

Answer 12

organization hierarchy:
- molecules, proteins, fats and carbohydrates form together to make up a cell
- multiple cells of the same type coordinate together to make up a tissue
- two or more different types of tissues come together to make up an organ
- multiple organs come together to make up an organ system
- all organ systems of the body work in concert to comprise the whole organism
definitions:
cell: the simplest structural unit of life; retains the functions and characteristics of life
- four main types of cells: muscle, neuron, connective and epithelial
- tissue: aggregates of differentiated cells with similar properties
- organs: composed of two or more types of tissues
- organ system: group of organs that work together to perform the same overall function

Question 13

Types of Cells

Answer 13

muscle cells: have intrinsic contractile properties that allow them to produce and relay force
* forms organs such as heart, skeletal muscle, and sphincters of the stomach and bladder
* make up the heart, can be found in blood vessels (many functions not just for local motion)

neurons: cells that initiate and conduct electrical signals, to allow for conscious and subconscious control of the body

epithelial cells: forms barriers to protect the body/organs
* selectively secretes/absorbs ions and organic molecules
* forms tissues that make up the skin, the lining of the GI tract, ducts and glands, etc.

connective tissue cells: connect, anchor, and support the structures of the body
* contributes to the formation of the extra-cellular matrix (ECM)

Question 14

Types of Muscle

Answer 14

muscle cells: all muscle cells generate mechanical force, however there are distinct differences between the three types of muscle cells
-> cardiac muscle, skeletal muscle and smooth muscle

Question 15

Neurons

Answer 15

neurons are excitable cells that have the ability to transmit electrical impulses
- these electrical impulses serve as signals for neurons to communicate with other neurons or tissues
- neurons do not look all the same; they exist in a variety of shapes and sizes within the body
- all neurons function in allowing for cell-to-cell communication
* excitable: a cell or tissue’s ability to respond to stimulation

Neurons are the functional unit of the nervous system
Glial cells are non-neuronal cells that support neurons
* note that gilial cells are not neurons, and are instead a type of connective tissue cell
* glial cells do not have the ability to transmit electrical impulses (type of connective tissue, part of the nervous system)
the connection between a neuron and another cell is called a synapse

Question 16

Neurons (body structure) - anatomy and definitions

Answer 16

soma: the cell body of a neuron
dendrites: long projection extending from the soma
- functioning in recieving incoming information and relaying it back to the soma
- has denritic spines that increase surface area
axon: a long process extending from the soma that relays outgoing signals to target cells (create synapse with another cell - axon termimals)
- begin at the axon hillock and ends at the axon terminal
myelin: a insulating sheath that forms over some neurons, that speeds up the transmission of an electrical signal down the axon (helps with having the least amount of signal)
- made up of 20-200 layers of plasma membrane
input (dendrites) -> soma -> (axon) output

Question 17

Neurons - myelin sheath and nodes of ranvier

Answer 17

two types of glial cells that create the myelin sheath:
- oligondendrocytes (CNS)
- schwann cells (PNS)
the myelin sheath is not continuous
- there are “gaps” in the sheath called the Nodes of Ranvier
- these nodes speed up the transmission of an electrical signal down the axon, and also conserves energy
- jumps from node to node

Question 18

Epithelial cells

Answer 18

epithelial cells are cells that are specialized for specific functions: selective secretion, absorption or ions/molecules and protection
- there are characterized and named according to their unique shapes and layers:
name by shape:
squamous - more flat/thin shape
cuboidal - cube shape
columnar - column shape
transitional - generally smaller than squamous cells but may change shape (as it stretched would look more like squamous than columnar)
name by layers:
simple - single cell layer
stratified - more than one cell layer
pseudostratified - single cell layer, but some cells overlap each other, giving the appearance of stratification

Question 19

Epithelial cells functions

Answer 19

epithelial cells are found in tissues that cover the body or individual organs
example: skin, nails, lining of the trachea, lining of the GI tract, parts of the female and male reproductive systems, part of the urinary system

generally, functions of epithelial tissues can be categorized as follows:
1. physical protection from chemicals, climate/dehydration, abrasion or mechanical injury or biological agents
2. to control permeability and maintain electrochemical gradients
A. also, to transmit or monitor the absorption and release of nutrients, waste products or other chemicals and molecules
3. enabling sensation - supports sensory neurons located in the skin, nose, mouth, eyes, and ears
4. produced specialized secretions
A. some epithelial cells are also gland cells, meaning they may produce secretions (example: mucus, sweat, saliva, gastric, enzymes, oil)

Question 20

Epithelial cells - apical side, basolateral side and basement membrane

Answer 20

epithelial cells rest on a basement membrane
each side of the epithelial cell can perform separate functions
* in this case the apical side of the cell is allowing for transport of glucose INTO the cell, while the basolateral side of the cell is allowing for transport of glucose OUT of the cell
* helps with compartmentalization
Apical side: the side of the epithelial cells that faces the lumen or external surface
basolateral (basal) side: the side of the epithelial cell that is anchored to the basement membrane
basement membrane: an extracellular protein layer that anchors the epithelial tissue

Question 21

Connective Tissue Cells

Answer 21

connective-tissue cells serve to connect, anchor and support the structures of the body; main functions:
* bind and support - ligaments, tendons, bones
* protect - bones and cartilage, adipose tissue, immune cells
* insulate - adipose tissue (fat tissue - protective because it cushions the body)
* transport - blood

there are many types of connective tissue cells, all of which serve a variety of functions. in general connective tissue consists of three primary constituents:
1. cells - eg. fibroblasts, macrophages, mast cells, plasma cells, adipocytes, leukocytes (main ones)
2. extracellular maxtrix (ECM) - comprised of fibrous proteins such as collagen and elastin
3. tissue fluid - comprised of ground substance, which is clear, viscous fluid containing proteoglycans

Question 22

Types of Connective Tissue

Answer 22

• there are six general categories of connective tissue including: loose connective tissue, dense connective tissue, cartilage, bone, blood and lymph

Question 23

Connective Tissue Proper - loose connective tissue and dense connective tissue

Answer 23

loose connective tissue:
* areolar tissue is present between the skin and muscle (fiber that create looose, open framework)
◦ contains both collagen and elastin fibers
◦ edema: areolar tissue swells with fluid
* adipose tissue is present deep to the skin (very important)
◦ important for insulation, energy storage, and protection (cushion/padding)
* reticular tissue provides the supporting framework for the kidneys, liver, spleen, lymph nodes and bone marrow

dense connective tissue (contains more closely-packed fibers than LCT):
* dense regular CT is present in tendons, ligaments and the dermis of the skin
◦ not well vascularized (not as close to blood vessels, you do not get as much nutrients transported to tissue and not allowing as much waste tissue to exit system)
* dense irregular CT is found in the dermis of the skin
◦ well vascularized (good blood flow)
* elastic CT is found in the walls of blood vessels, as well in the ligaments between the vertebrae (has more elastin in it, which allows for more stretch in the tissues, first two are not as stretchy)

Question 24

Fluid connective tissue - blood and lymph

Answer 24

fluid connective tissues have distinctive population of cells suspended in a watery matrix that contains dissolved proteins
Blood:
* A type of fluid connective tissue that functions to transport nutrient, gases and metabolic waste products
* composed of:
◦ platelets, and red and white blood cells (45%)
◦ plasma (55%)
* move through blood vessels
◦ arteries, arterioles, capillaries, venules, veins
- blood flowing through cardiovascular system
Lymph:
* a type of fluid connective tissue that functions to drain tissue fluid (drain excess fluid from tissue)
* composed of:
◦ lymph fluid (interstitial fluid)
◦ white blood cells
◦ ions, organic molecules, cellular debris, proteins, etc.
* moves through lymphatic vessels
- flows within lymphatic system

Question 25

Supporting Connective Tissues - cartilage and bone

Answer 25

cartilage:
* chondrocytes: mature cartilage cells that produce collagen to form a cartilage matrix
* is avascular (long healing time), and thus has a relatively longer healing time after injury
* primarily functions to support other structures
◦ hyaline cartilage: present at the end of long bones, between the ribs and sternum, the trachea, larynx and bronchi
◦ elastic cartilage: present in the external ear and larynx
◦ fibrous cartilage: present in intervertebral disks, pubic symphysis, and in the knee joint
* bone heals much quicker as compared to cartilage as cartilage is not well vascularized
bone:
* bone tissue is a solid, crystalline matrix made from calcium salts and collagen fibers
◦ ~2% bone cells
◦ ~65% matrix
◦ ~33% collagen fibers
* is very well vascularized