Animal form (morphology) and Functions (physiology) 1

adaptations

heritable traits that allow some individuals to survive and reproduce in certain environments better than others (higher fitness)

what do physical laws do

(mechanical strength, diffusion, heat exchange) constrain

these adaptations and lead to convergent evolution

what has a big effect on how animals work

body size

what does Increasing complexity of large multicellular animals impose

“design

constraints” on body form and function

thermoregulation

an example of homeostasis integrating form

(morphology), function (physiology) and behaviour

all animals exchange what with their environment

materials ( nutrients, gases, waste, heat, etc)

Why can small organisms exchange materials directly with their environment?

- large surface area relative to volume

(or mass)

- short diffusion distance between

environment and cell(s)

Why can't large organisms rely only on diffusion?

They have a low surface area-to-volume ratio and long diffusion distances

How do specialized surfaces improve exchange?

Branching and folding increase surface area, allowing more materials to be exchanged

What are the two specialized fluids?

Blood and interstitial fluid.

What connects individual cells to the environment?

Specialized transport systems and specialized fluids.

Hierarchical organisation of complex animals

Cells make us tissues which are organised into functional units (organs)

and groups of organs work together (organ systems)

What are the four main tissue types in animals?

Epithelial, connective, muscle, and nervous tissue.

What is the function of connective tissue?

Supports, connects, protects, and transports materials

what type of connective tissue is blood

fluid connecting tissue

what kind of connective tissue is tendons

dense connective tissue

what kind of connective tissue is the extracellular matrix

loose connective tissue

what kind of connective tissue is bone

hard supporting connective tissue

epithelial tissue

Covers body surfaces, lines organs, and allows exchange and absorption.

nervous tissue

Nerve cells or neurons

transmit electrical signals

muscle tissue

Skeletal, cardiac, and smooth

What are the 3 hormone families?

Protein/peptide, amino acid derivatives, and steroids.

lipid solubility

How the hormone interacts with (stimulates) the target/effector cell depends

on whether the hormone passes easily through the plasma membrane

What are the important examples/exceptions?

• Protein: secretin.

• Monoamine: adrenaline (surface receptor).

• Thyroid: lipid-soluble (inside receptor).

• Steroid: cortisol (inside receptor).

1. How do water-soluble vs. fat-soluble hormones work?

• Water-soluble: Travel freely in blood → bind surface receptors → signal transduction.

• Fat-soluble: Travel attached to proteins → enter cells → bind internal receptors → regulate genes.

How do their storage and transport differ?

• Water-soluble: Stored in vesicles; travel freely in blood.

• Fat-soluble: Usually made when needed; travel attached to transport proteins.

negative feedback

- tends to maintain constant or

“baseline” levels of hormones

(though the absolute regulated

level of hormone can vary

markedly)

positive feedback

-amplifies a certain stimulus until a certain change occurs

- important for “explosive” events

- oxytocin, prolactin at birth

- estradiol at ovulation

what work together to maintain peripheral endocrine organs

hypothalamus and pituitary

Posterior vs. anterior pituitary?

• Posterior: Long axon neurosecretory cells; releases ADH and oxytocin made by hypothalamus.

• Anterior: Short axon neurosecretory cells +

  specialised (portal) blood system; produces and releases its own hormones.

Know the main anterior pituitary hormones:

• ACTH = stress (stimulates adrenal glands)

• FSH/LH = reproduction

• GH = growth

• PRL = milk production

• TSH = thyroid stimulation (thyroxine)

Short-term vs. long-term stress response?

• Short-term: Hypothalamus → nerve signals → adrenal medulla → epinephrine/norepinephrine.

• Long-term: Hypothalamus → CRH → anterior pituitary → ACTH → adrenal cortex → cortisol.

What are the functions of the stress hormones?

• Epinephrine/norepinephrine = immediate fight-or-flight.

• Cortisol = maintains energy and increases blood glucose during prolonged stress.

adrenal gland hormones

-adrenaline: triggers short term fight or flight response

-cortisol: short term and long term stress

-aldosterone: increases reapsorption of sodium by the kidneys

What does PTTH do?

-released by the corpora cardiaca

-(protein hormone) that stimulates the prothoracic gland to release ecdysteroid (steroid) , which triggers molting.

What does Juvenile Hormone (JH) do?

• it is released by the corpora allata

• Maintains larval characteristics and prevents the insect from becoming an adult.

How does JH control metamorphosis?

• High JH: Larva → another larval stage.

• Low JH: Larva → pupa.

• No JH: Pupa → adult.

action potential

-electrical signal

-A rapid, transient change in

membrane potential

direction of signal In a neuron

Dendrites → Cell body → Axon hillock → Axon → Synaptic terminals → Next cell.

what does Movement of substances across membranes depends

on

1) Selective permeability of lipid bilayer (diffusion)

2) Transmembrane proteins that transport selected ions and molecules

by facilitated diffusion and active transport

What are ligand-gated channels?

Channels that open when a specific chemical messenger (ligand) binds to them.

What are voltage-gated channels?

Channels that open or close in response to changes in membrane potential (electrical charge).

what is membrane potential due to

This is due to Selective permeability as well as Active transport

(the Na-K pump)

How does membrane permeability change to cause this

change in membrane potential

Voltage-gated ion

channels …

open and close by

changing shape

(conformation) ….

in relation to changes in

m.p. or voltage difference

how is action potential generated

Voltage-gated ion channels change membrane permeability

to generate an action potential (electrical signal)

what are the steps of action potential

1. resting state

2. depolarization

3. rising phase

4. repolarization

5. hypepolarization

6. return to resting potential

resting state

-around -65mv

• Voltage-gated Na+ and K+ ion channels are closed

• Non-gated channels maintain resting membrane potential

-OUTWARD diffusion of K+ via open resting (“leak”) K channels

-Little INWARD diffusion of Na+ due to few open resting Na channels

-Inside becomes negative due to net loss of K+ (until equilibrium reached

depolarization

initial depolarisation opens some voltage-gated Na channels allowing Na+ to diffuse in

• inside becomes more positive

rising phase

-if depolarization reaches threshold (about -55mv)

• then all voltage-gated Na channels open (positive feedback Hodgkin cycle)

• +30mV

repolarization

-Voltage-gated Na⁺ channels inactivate, and voltage-gated K⁺ channels open, allowing K⁺ to leave the cell

-inside becomes negative (-65mV)

hyper polarization

K⁺ channels close slowly, so extra K⁺ leaves. Inside becomes temporarily more negative than resting potential. (-80mV)

return to resting potential

K⁺ channels close and the neuron returns to its resting state. (-65mV)

So selective permeability and changes in

permeability over time are…

the basis of electrical

signaling in the nervous system

How do action potentials carry information?

Electrical signals start at one point on the membrane and travel along the axon to transmit information to other cells.

why do action potential propegate

-charge spreads down the membrane

-Current spreads in both directions along axon

why does action potential only move in one direction

because Na channels “behind”

the a.p. site are inactive for short period =

refractory period

how is axon speed determined

speed at which action potentials are conducted is

proportional to axon diameter

what speeds up action potential

Schwann cells and myelin sheath (insulation) allow for

saltatory (more rapid) conductance of action potential

what are glial cells

support, protect, and nourish neurons

where are schwann cells located

glial cells

in peripheral NS (PNS)

where are Oligodendrocytes located

lial

cells in central NS (CNS)

Voltage-gated ion channels

restricted to…

nodes of ranvier

How does saltatory conduction work?

• Inward current during a.p. is

transmitted all the way to the

next node (because of

Schwann cell insulation)

• Depolarises membrane at

next node to threshold and

regenerates a.p.

where and how do neurons meet and transfer info

at the synapse through neurotransmitters

synapse process

1. A.p. arriving at synapse depolarises pre-synaptic membrane

2. voltage- gated Ca channels open, Ca influx

3. synaptic vesicles move to and fuse with presynaptic membrane, release neurotransmitter into synaptic cleft

4. neurotransmitter binds to ligand-gated ion channels on post-synaptic membrane and change m.p.

what is graded potential and what is it poportional to

-Results in change in membrane potential of post-synaptic cell

-poportional to the size of the stimulus

parasympathetic

rest and digest

-slow heartbeat

-stimulate stomach digestion

sympathetic

fight or flight

-increase heartbeat

-inhibit activity of the stomach