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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