Ch 33 the animal body: basic form and function

homeostasis

internal balance/ “steady state” that organisms maintain to regulate their internal environment despite external changes.

homeostatic processes involve

behavior, physiology, physical adaptations

the overall flow and transformation of energy in an animal

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

bioenergetics

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

basal metabolic rate

a physiological state in which activity is low and metabolism decreases

enables animals to save energy while avoiding difficult and dangerous conditions

torpor

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

hibernation

enables animals to survive long periods of high temperatures and scarce water

estivation/summer torpor

exhibited by many small mammals and birds during part of the day that is coldest

daily torpor

A biological mechanism that counteracts changes in body conditions by triggering responses that restore balance

negative feedback loop

A biological mechanism that amplifies changes in body conditions by triggering responses that enhance the initial stimulus.

positive feedback look

blood sugar leveling: NFL

food is consumed and digested, causing blood glucose levels to rise → in response to higher glucose levels, the pancreas secretes insulin into the blood → in response to higher insulin levels, glucose is transported into cells and liver cells store glucose as glycogen. As a result, glucose levels drop → in response to the lower concentration of glucose, the pancreas stops secreting insulin → repeat

child birth: PFL

baby pushes against the cervix → stretching of the cervix causes nerve impulses to be sent to the brain → the brain stimulates the pituitary to release oxytocin → oxytocin causes the uterus to contract → repeat, contract increase in frequency and intensity

acclimatization

the process by which an organism adjusts to changes in its environment, enabling it to maintain performance across a range of conditions.

examples: Everest BC, Olympic athletes

thermoregulation is controlled by the

hypothalamus

4 ways heat is exchanged

conduction, convection, radiation, evaporation

5 adaptations that help animals thermoregulate

insulation, behavioral, circulatory adaptations, cooling by evaporative heat loss, adjusting metabolic heat production

animals that generate heat by metabolism (birds/mammals)

can maintain a stable body temperature despite fluctuations in external temperature

more energetically expensive

endothermic animals

animals that gain heat from external sources (most invertebrates, fishes, amphibians)

rely on their environment for body temperature

ectothermic animals

epithelial tissues

A type of tissue that covers surfaces, lines cavities, and forms glands in the body

connective tissues

connect tissues together and provide support

muscle tissues

A type of tissue responsible for movement in the body, consisting of cells that can contract and relax.

nervous tissues

A type of tissue that transmits electrical signals between different parts of the body, facilitating communication and coordination.

classified by number of layers and shape of the cell

single or multiple layers

cell shapes: squamous, cuboidal, columnar, transitional

arrangement can be simple (single cell layer), stratified (multiple tiers of cell), or pseudostratified (a single layer of cells of varying length)

epithelial cells (cont’d)

fibroblasts

are a type of cell found in connective tissue that produce collagen and other fibers, playing a crucial role in wound healing and tissue repair.

cells embedded in a non-cellular matrix

consist of fibroblasts

ground substance usually contains some combination of collagen, elastic, or reticular fibers

used to connect different tissues or give the body structure

types: loose/areolar, dense/fibrous, cartilage, bone, adipose, blood

connective tissues

3 types of muscle tissue

skeletal (voluntary. striated), smooth (involuntary, no striations), cardiac (involuntary, striated, intercalated discs)

functions in the receipt, processing, and transmission of information

contains: neurons, glial cells

nervous system

the neuron

• main cell in the NS

• specialized to receive and transmit electrical impulses

• consists of: cell body, dendrites, axon, astrocyte, oligodendrocyte, axon terminals, myelin sheath

• 4 main types according to number and placement of axons and dendrites (unipolar, bipolar, multipolar, pseudounipolar)

Cell body (neuron anatomy)

large structure with central nucleus

dendrites

Short, branched extensions of a neuron that receive signals from other neurons.

axon

long projection from the cell body; specialized in transmitting impulses

astrocyte

type of glial cell that regulates the chemical environment of the nerve cell

oligodendrocyte

type of glial cell that insulates the axon so the electrical nerve impulse is transferred more efficiently (cells that make up the myelin)

myelin sheath

fatty covering that insulates the axon and makes neuronal signaling more efficient (Single segment of the multicellular membrane structure)

axon terminals

endings of axons through which axons make synaptic contacts with other neurons

(1) unipolar

(2) multipolar

(3) bipolar

(4) pseudounipolar

• provide essential structural support, nutrition, insulation, and immune defense (don’t perform neural activity)

• outnumber neurons (10:1)

• mutations in these cells are the top cause for brain tumors

• examples: microglial cell, astrocyte, oligodendrocyte, ependymal cell

glial cells

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

charged cellular membrane of neuron

321 NOKIA

3 Na+ out

2 K in

1 ATP

• Resting state

  • inside of neuron = negative

  • outside of neuron = positive

• Depolarization

  • stimulus triggers opening of Na+ channels

  • Na+ flows into the cell

  • inside becomes positive

• Repolarization

  • influx of positive Na+ ions triggers K pumps to open

  • Na+ channels close, K + channels open

  • K+ leaves the cell

  • inside becomes negative again

• Signal moves forward

  • positive charge spreads to the next section

  • that triggers Na+ channels ahead to open

  • action potential continues to travel down the axon

  • domino effect

chemical synapse

• depolarization causes voltage-gates 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 vesicle with 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