Chapter I

Homeostasis

Homeostasis - is the ability of the body to maintain a relatively constant internal

environment.

- it is a coordinated response

- control of homeostasis includes primarily: the Nervous System and the

Endocrine System.

- together they comprise both an electrical (by way of impulse) and chemical (hormonal) response.

An important factor in maintaining homeostasis is the involvement of body fluids which consist of H2O and dissolved chemicals.

Body Fluids – the main focus of homeostasis is maintaining the volume and composition of fluids throughout the body.

Intracellular fluid (ICF) - fluids found within the cells.

Extracellular fluid (ECF) – fluids found outside of cells.

There are different types of ECF:

1. interstitial fluid – found between cells

2. blood plasma – inside blood vessels between cells

3. lymph – fluid found inside lymphatic vessels

4. cerebrospinal fluid (CSF) – around brain and spinal cord

5. synovial fluid – inside joint capsules

6. aqueous humor – inside anterior eye

7. vitreous body – inside posterior eye

The internal environment refers to the interstitial fluid throughout the body

specifically cells of the body.

- their fluid composition changes as fluids are exchanged between

blood vessels and the internal environment

- most or all exchanges occur at capillaries: - O2

- nutrients and minerals

- waste

Control of Homeostasis – Homeostasis is affected by both major and minor

disruptions.

Major – injury, poisoning, extreme temperatures

Minor – skipping meals, exertion, stress

disruptions – change in the chemical composition due to

changes in external or internal environment.

Regulation of homeostasis occurs through feedback systems

Feedback Systems – information about a homeostatic response that is sent

back to the integrating center.

- the feedback system constantly monitors, evaluates, alters, and re-evaluates the condition and the response to it.

Three components of feedback systems:

1. Receptor – continually monitors its environment

- when alerted to a change it sends out a

signal

- involves nerves and endocrine organs

2. Control Center – receives information about the change

and decides on the appropriate response

- usually lies within the CNS

- can also be endocrine cells

- receives input, interprets info, sends out

response.

3. Effector – the part of the body that carries out the

response

- can be muscle, gland, tissue etc.

There are 2 Types of Feedback Systems:

1. Negative Feedback – (a majority of the responses)

- reverses the original stimulus

- receptors in certain areas receive message

- input by way of impulses travel to control center

- control center interprets message and sends out

impulse

- impulse goes to effector

- response decreases stimulus

- return to homeostasis

e.g. Blood Pressure, Blood Sugar, Body Temp. etc.

2. Positive Feedback – (usually occurs during special

events)

- a response enhances original stimulus

- receptors are alerted to a change in homeostasis

- input by way of impulses travel to control center

- control center interprets message and sends out

impulses

- impulse goes to effector

- response enhances or amplifies original stimulus

- return to homeostasis

e.g. uterine contractions, loss of blood etc.

Anatomical Terminology

Anatomical Position – standing position, palms and feet facing forward

- if not standing: -prone (face down)

-supine (face up)

Regional Names: 1. Head- cranial; facial (skull, face)

2. Neck – cervical

3. Trunk – thoracic (chest); abdomen, pelvis

4. Upper Limbs – arms, wrists, hands

5. Lower Limbs – buttocks, thigh, knees, legs, feet

Directional Terms: Superior – towards the head

Inferior – away from the head

Anterior – closer to front of body

Posterior – closer to back of body

Medial – close to midline of body

Lateral – away from midline of body

Intermediate – between two parts or structures

Ipsilateral – on the same side

Contralateral – on the opposite side

Proximal – near to the point of origin

Distal far from the point of origin

Superficial – toward surface

Deep – away from surface

Planes and Sections

Planes – imaginary flat surfaces that pass through body parts.

1. Sagittal Plane – plane that passes vertically through the

body

- usually divides body into left and right

midsagittal – equal left and right

parasagittal – unequal left and right

2. Frontal (coronal) – divides body into anterior and posterior

3. Transverse (horizontal) – divides body into superior and inferior

4. Oblique – passes through body at an angle

Body Cavities – spaces within the body that house internal organs

-have three functions: protect

support

separates

The 2 Main Cavities: 1. Dorsal Cavity – a.)cranial cavity

b.)vertebral cavity

2. Ventral Cavity – a.) Thoracic cavity (composed of 3 cavities):

i) pleural cavity

ii) pericardial

iii) mediastinum

b.) Abdominal cavity (composed of 2 cavities):

i) abdominal cavity

ii) pelvic cavity

Membranes – thin sheets of epithelial tissue and connective tissue that surrounds the organs and cavities.

- also referred to as serous (usually secretes a small amount of fluid to lubricate cavities and organs to prevent friction.

Membranes are divided into 2 layers: Visceral – surrounds organs

Parietal – lines cavities

e.g. pleural cavities – pleura: visceral (lungs)

parietal (pleural cavity)

pericardial cavity – pericardium: visceral (heart)

parietal (chest wall)

abdominal cavity – peritoneum: visceral (around most organs of the abdominal cavity)

parietal (along diaphragm) and abdominal wall

retroperitoneal (between visceral layer and back of abdominal cavity) – kidneys, pancreas, duodenum, ascending and descending colon, and abdominal aorta and inferior vena cava

Systems of The Body:

There are 11 systems.

They work together to form the human body.

1. Endocrine –hormone delivery and production

2. Lymphatic- immune response and drainage of extracellular fluid

3. Cardiovascular- blood transport, gas exchange, waste transport

4. Respiratory- gas exchange

5. Muscular- movement, body temperature regulation

6. Skeletal-movement, protection, blood production

7. Nervous- sensory and motor

8. Reproductive- creation of new individuals

9. Digestive- ingestion, breakdown, absorption and elimination

10. Urinary- elimination of liquid waste, filtration

11. Integumentary- skin, hair, nails, glands