BIOL Chapter 33

Animal form and function

homeostasis

organisms use this to maintain a steady state or internal balance regardless of environment

ex: humans- body temp, blood pH, glucose concentration

factors to consider in homeostasis

1. Organisms are OPEN systems- constant exchange with environment

2. Organisms energy requirements

3. Process involve: physical adaptations, behavior, physiology

bioenergetics

overall flow and transformation of energy in an animal

determines how much food an animal needs and it relates to an animal’s size, activity, and environment

Basal metabolic rate

average amount of energy used by an organism in a non-active state

based on mass (smaller mass, higher metabolic rate)

torpor

physiological state in which activity is low and metabolism decreases

allows animals to save energy while avoiding difficult and dangerous conditions

daily torpor exhibited by many small mammals and birds during parts of the day that is coldest

hibernation

long-term torpor that is an adaptation to winter cold and food scarcity

estivation

summer torpor- allows animals to survive long periods of high temps and scarce water

homeostasis mechanism

fluctuations above or below a set point- stimulus

• detected by a sensor and triggered by a response

response returns variable to set point

ex: speeding until you see a cop and you drive to set point (speed limit)

negative feedback

homeostasis tends to be this loop, returning to normal range

• ex: blood sugar levels- increase when eating, decrease once insulin is released

positive feedback

not typically homeostasis, amplifies a stimulus

• oxytocin release increases during pregnancy as baby pushes against the cervix increases

acclimatization

body adjusting to conditions

• increasing RBCs at higher altitudes

EPO

erythropoietin stimulates productions of RBCs in bone marrow, after EPO treatment, more immature RFBCs are detectable and maximum oxygen uptake is enhanced

Thermoregulation

relatively constant internal temperature to keep enzymes efficient and avoid denaturation

controlled by hypothalamus

heat exchange by

• radiation

• convection

• conduction

• evaporation

Integumentary system

skin, hair, sweat glands

often involved in heat regulation

Thermoregulation adaptations

1. insulation

2. behavioral responses

3. circulatory adaptations

4. cooling with evaporative heat loss

5. adjusting metabolic heat production

insulation

• skin, feathers, fur and blubber reduce heat flow between animal and environment

• important in marine animals such as whales and walruses

thermoregulation: circulatory adaptations

regulation of blood flow near body surface

endotherms and some ectoderms can alter amount of blood flow between body core and skin

vasodilation and vasoconstriction

• countercurrent exchange

vasodilation

blood flow in skin increases, facilitating heat loss

vasoconstriction

blood flow in skin decreases, lowering heat loss

countercurrent exchange

a circulatory adaptation

transfers heat between fluids going in opposite directions, reducing heat loss

arranged in many marine mammals, birds, some bony fishes, sharks, and endothermic insects (in the thorax)

evaporative heat loss

many animals lose heat by evaporating water on their skin

sweating/bathing moistens skin

panting increases the cooling effect in birds and many mammals

thermoregulation behavior responses

• both endotherms and ectotherms use

• some terrestrial invertebrates have postures that minimize or maximize absorption of solar heat

  • dragonflies point their rear end towards the sun when its warm

• honeybees huddle together during cold weather to retain heat

thermogenesis

adjustment of metabolic heat production to maintain body temp

increased by muscle activity such as moving or shivering

• mother python wrapping eggs

nonshivering- mitochondria activity increases

some ectotherms also shiver

seasonal acclimatization

birds and mammals can vary their insultation

subzero- some ectotherms produce antifreeze compounds to prevent ice formation

hypothalamus

controls thermoregulation

in brain

fever

response to some infections, reflects an increase in the normal range for the biological thermostat

some ectothermic organisms seek warmer environments to increase body temp. in response to certain infections

physiological thermostat

endothermic

animals generate heat by metabolism

birds and mammals

can maintain a stable body temp even with large environmental fluctuations

however, more energetically expensive

ectothermic

animals gain heat from external sources

most invertebrates, fishes, amphibians

main types of tissue

1. epithelial

2. connective

3. muscle

4. nervous

epithelial tissue

line cavities, open spaces and surfaces

classified from number of layers and cell shape

single layer - simple

multiple- stratified

squamous epithelial

flat, irregular, round shape

simple: alveoli, capillaries

stratified: skin, mouth, v*gina

cuboidal epithelial

cube shaped, central nucleus

glands, renal tubules

columnar epithelial

tall, narrow, nucleus towards base, tall narrow nucleus along cell

simple: digestive tract

pseudostratified: respiratory tract (single layer of cells of varying length)

transitional epithelial

round, simple but appear stratified

urinary bladder

connective tissue

• Connect tissues together, provide support

consists of fibroblasts embedded in a non-cellular matrix

ground substance consists of: collagen, elastic, or reticular fibers

use to connect tissues or give body structure (ex: blood has a unique function)

muscular tissue

Three kinds of muscle tissue:

• Skeletal – voluntary, striated

• Smooth – involuntary, no striations

• Cardiac – involuntary, striated, intercalated discs

muscular tissue contraction

Nervous tissues

• Nervous tissue functions in the receipt, processing, and transmission of information

• Nervous tissue contains

  • Neurons, or nerve cells, that transmit nerve impulses

  • Glial cells, or glia, support cells

Neuron

• The main cell of the nervous system is the neuron

• Neurons are specialized to receive and transmit electrical impulses

Neuron structure

Cell body - large structure with a central nucleus

Dendrites - projections from the cell body; specialized in receiving input

Axon - projection from the cell body; specialized in transmitting

Impulses

Astrocyte - regulate the chemical environment of the nerve cell

Oligodendrocyte - insulate the axon so the electrical nerve impulse is transferred more efficiently

Axon terminals -  endings of axons through which axons make synaptic contacts with other nerve cells

neuron transmission

glial cells

• Support, protect and nourish neurons

• Outnumber neurons (10 to 1) in the brain

• Fulfill many vital functions

• Most brain tumors caused by mutations in glia

neuron communication

• Signals are possible because each neuron has a charged cellular membrane (a voltage difference between the inside and the outside).

• The charge of this membrane can change in response to neurotransmitter molecules released from other neurons and environmental stimuli.

chemical synapse

• Depolarization causes voltage-gated Ca²⁺ channels to open. 

• Calcium ions initiate a signaling cascade that causes synaptic vesicles, containing neurotransmitter molecules, to fuse with the presynaptic membrane. 

• Fusion of a vesicle with the presynaptic membrane causes neurotransmitter to be released into the synaptic cleft.

• Once neurotransmission has occurred, the neurotransmitter must be removed from the synaptic cleft so the postsynaptic membrane can “reset” and be ready to receive another signal.