Animal Phys Midterm 3 review pt 1

Skeletal Muscle

• Attaches to skeleton through tendons

• Voluntary control

• Striated / multi nucleated

Cardiac Muscle

• Composes heart wall

• Involuntary control

• Uni nucleated

Smooth muscle

• Lines hollow visceral organs (stomach, uterus, arterioles)

• Involuntary control

• Uni nucleated, not striated

Characteristics of Muscle

Excitability, Contractility, Extensibility, Elasticity

Sliding filament theory

Muscles contract when thin protein filaments slide inward over thick protein filaments shortening the basic contractile unit of the muscle fiber without changing the actual length of the filament

Muscle

Organized collection of muscle fascicles bound together by connective tissue

Fascicle

Set of muscle fibers bound by connective tissue

Muscle fiber

Skeletal muscle cell

Muscle contraction trigger

Nerve impulse causes calcium ions to be released inside the muscle cell

Uncovering binding sites (Muscle contraction)

Calcium binds to troponin, causing tropomyosin to shift and expose the active bindings sites on the actin filament

Power Stroke (Muscle contraction)

Powered by the breakdown of ATP, the myosin head bends and pulls the actin filament toward the center of the sacromere

Release and Reset (Muscle Contraction)

A new ATP molecule binds to the myosin head, causing it to detach from actin. The ATP splits, re-energizing the myosin head so it can grab the next site further down the actin chain.

Myofibrils contain myofilaments

Actin (Thin filament)

Myosin (Thick filament)

Sum of sacromere shortening

Sum of sarcomere shortening is the amount the myofibril shortens

Sarcomere length-force relationship: Ascending Limb

• Thin actin filaments from opposite ends of the sarcomere begin to overlap and interfere with one another, while thick myosin filaments bump up against the Z-discs. This spatial distortion blocks myosin heads from binding effectively to actin, reducing total force production

Sarcomere length-force relationship: Optimal Length Plateau

• Maximal

• the ideal resting state where there is optimal overlap between actin and myosin. Nearly all available myosin heads can bind to actin, maximizing the formation of force-producing cross-bridges

Sarcomere length-force relationship: Descending Limb

• Actin and myosin filaments are pulled apart. Fewer myosin heads can reach or overlap with actin binding sites, causing active force to drop off. If stretched far enough that all contact is lost, active force falls to zero

Muscle Contractions - Isometric

Same length, no shortening (lift a car)

• muscle generates force and tension without any observable change in muscle length or joint movement

Muscle Contractions - Isotonic

same tension, shortening (lift a book)

• muscle changes its length while moving a load against a relatively constant tension

Muscle Fiber types: Fast twitch

quick, explosive, actions. Anaerobic.

Little myoglobin

Slow twitch

slower, aerobic. Lots myoglobin

Which twitch can deliver more force?

Fast twitch can deliver 10x more force than slow twitch!

Is white meat fast or slow twitch?

Fast twitch

Is dark meat slow twitch or fast twitch?

Slow twitch, lots of myoglobin

How do air sacs help birds in flight?

Air sacs minimize the energy soaring birds need for wing muscles

• provide massive amounts of oxygen for high-energy flight, reducing body weight, and even assisting with physical flight mechanic

What type of skeletal system do vertebrates, insects, and crustaceans have?

Rigid skeleton

What kind of skeletal system is found in worms, octopus, spider legs, vertebrate tongues, and elephant tongues?

Hydrostatic skeleton

Endoskeleton

found in Vertebrates

Exoskeleton

Found in insects

Fluid + soft walls

Found in worms and octopus

Fluid + rigid elements

Spider legs

Muscles as walls and fluid

Vertebrate tongues and elephant trunks

Rigid skeleton

• Two basic forms (endo-, exo-) that serve the same basic role, provide structure

• Typically a muscle spans a joint where two bones meet and thus creates a mechanical movement

Hydrostatic skeleton

• Typically a chamber with flexible walls that’s filled with water or body fluid

• Walls contain muscles that attach to one another with connective tissue

• When muscles contract they create a tension in the walls that pressurizes the fluid

How do spiders extend their legs?

Hydraulic force

• Since they have flexor muscles to contract the legs but no extensor muscles to extend the legs

Amoeboid movement

• Movement of these cells associated with cytoplasmic streaming, change in cell shape, extension of pseudopodia

• Some protozoans, slime molds, and

  vertebrate white blood

Cilia

usually thousands. Movements parallel to the surface that bears the cilia. Movement of small organisms and inside of big organisms

Flagella

usually one or a few. Movement parallel to the flagella. For movement of some single cell organisms as well as sperm.

Nervous system

• Exerts point-to-point control through nerves

• Electrical, chemical in nature

• Like a phone

One of the two systems that regulates all physiological processes

Endocrine system

• Broadcasts to essentially all cells

• Secretion of chemicals into blood, extracellular fluid

• Like a radio

One of the two systems that regulates all physiological processes

Why are chemical messengers important?

• Development

• Homeostasis

• Disruptive events (stress)

• Social interactions

First Endocrine study

German scientist Berthold castrated roosters and noted the lack of development of wattles, combs and males sex behavior

First Demonstration of Hormone Replacement in Humans

French physician Brown-Séquard injected himself with aqueous extracts of testes from dogs and guinea-pigs

What were the problems with Brown Sequard’s experiment?

Placebo effect and no controls

Endocrine signaling: First step

Hormone released by signaling cell in a gland into extracellular environment

Endocrine signaling: Second step

Hormone transported in circulatory system

Endocrine signaling: Third step

Hormone interacts with target cells (those that

have receptors)

Exocrine gland

chemical signals released outside animal

Endocrine gland

chemical signals released into circulation

Endocrine organs

• Hypothalamus

• Pituitary

• Thyroid and Parathyroid

• Adrenal

• Pancreas

• Ovaries

• Testes

Autocrine

Cellular secretions that affect the cell itself

Paracrine

Cellular secretions that affect neighbor cells

Endocrine

Chemical produced in one location in the body that have effects on cells elsewhere

Ectocrine (exocrine) - Pheromones

within species chemical cues

Ectocrine (exocrine) - Kairomones

among species chemical cues

Different types of Endocrine effects

• Direct cell signaling

• Autocrine and Paracrine signaling

• Endocrine signaling

• Neural signaling

What are the 4 chemical groups of hormones?

• Proteins, peptides

• Modified amino acids

• Steroids

• Modified fatty acids

Different types of hormones

• Epinephrine (amine)

• Insulin (peptide)

• Testosterone (steroid)

• Prostaglandin (modified fatty acid)

Peptide / protein hormone synthesis

• products of translation

• often must be processed to active form

Peptide / protein hormone Secretion

• Sometimes stored, sometimes not

• Regulated

Steroid synthesis

enzyme action on cholesterol precursor

Steroid Secretion

• Constitutive only (cannot be stored)

• Usually regulated

Modified amino acid and fatty acid synthesis and secretion

Modified by enzymatic action and released into

circulation

What do Hormones do?

• Organizational Roles

• Activational Roles

Organizational Roles of Hormones

Hormones are important in regulating the phenotype of a developing vertebrate

• Hormones affect body structure and the organization of the brain

Organizational role of androgens in dogs

Neutering males before they grow up will make then sit and pee like females instead of lifting a leg

Activational Role of Hormones

In adult organisms after hormones have organized the body, hormones activate physiological processes at the cellular level

Organization vs Activiation

Hormones during development organize the brain such that it is sensitive to the activational actions of hormones during adult life

Where do hormone interactions occur?

• Sensory systems

• Central nervous system

• Effectors (ex. muscles)

• Behavior

What regulates synthesis and secretion of hormones?

• Direct effects - environmental cues

• Signalized effects - mediated through CNS

• Feedback - endocrine system (homeostasis)

Negative feedback

A regulatory mechanism in which the output of a system acts to oppose or reduce the initial change, helping the system maintain stability, equilibrium, or Homeostasis.

• Almost every hormone is regulated through negative feedback

Negative feedback example

Cortisol inhibiting the hypothalamus and anterior pituitary once enough has been produced, inhibiting more cortisol production

Positive feedback

a self-reinforcing process where a system's response amplifies and accelerates the initial change or stimulus, moving the system further away from its starting state until a specific endpoint is reached

Positive feedback example

During ovulation, progesterone stimulates the pituitary gland to produce more LH to stimulate the production of more progesterone

Common properties of hormone receptors

1. High specificity

2. High Affinity

3. Low capacity

Intracellular Steroid receptors

specialized intracellular proteins located in the cytoplasm or nucleus of target cells that bind lipophilic steroid hormones to regulate gene expression

• Slow acting

How do Hormones exert effects?

Peptide hormones bind to membrane bound receptors » Fast acting

• Necessary for the regulation of fast change in physiological processes

Anterior pituitary

the front lobe of the pituitary gland, the hypothalamus sends releasing or inhibiting hormones through these blood vessels to signal the anterior lobe

• Hypophysiotropic hormones cause release of pituitary hormones into the circulatory system

Posterior pituitary

does not manufacture its own hormones Instead, hormones are synthesized by the hypothalamus, transported down nerve axons, and stored/released into the bloodstream upon neural signals

Hypothalamus

• Neurons of the hypothalamus receive stimulatory and inhibitory neural inputs

• Influence the secretion of hypophyiotropic hormones

Oxytocin and Vassopressin

Two hormones secreted by the posterior pituitary that are synthesized in the hypothalamus

Oxytocin function

Contraction of the smooth muscles in the reproductive tract (childbirth, egg laying, ejaculation, etc.) and mammary glands (lactation)

Vasopressin - low levels

Antidiuretic action on kidneys helps retention of water (induces expression of aquaporins in collecting duct of kidneys)

Vasopressin (high levels)

Increase in blood pressure (constricts blood vessels) and increase in glomerular filtration rate (getting rid of water)

Median eminence (infundibulum)

• Connects hypothalamus and anterior pituitary

• Contains portal vessels through which hormones flow to anterior pituitary

Hypophysiotropic hormones

• Releasing hormones: from hypothalamus and trigger the anterior pituitary

• Stimulating hormones: from the anterior pituitary and trigger the peripheral gland

Why have these hypophysiotropic axes?

• Collecting sensory information

• Each step magnifies the signal

• The brain can have large results from small signals » Endocrine Cascade

Endocrine disrupters

Can block or mimic actions of natural hormones

The Disappearing Male

Biphenol A (BPA) acts as an endocrine disrupter, blocking androgen (testosterone) signaling and interfering with normal male development, including lower sperm count and sperm abnormalities. It increases the risk for testicular cancer, genital deformities, and even disorders like cerebral palsy, autism, ADHD, dyslexia, and Tourettes.

Environmental estrogens

• Chemicals that ‘look’ and ‘act’ like estrogens to the receptors

• Some will block or activate the receptor, either way affects the endocrine system adversely

Phytoestrogen

One of the first environmental estrogens that are found in plants and thought to be an evolutionary response to predation

Endocrine disruptor examples

• Atrazine

• DDT

• Diethylstilbestrol (DES)

Diethylstilbestrol (DES)

A super estrogen that was prescribed to women to deal with morning sickness

• Caused a lot of babies to develop abnormally

• Caused higher miscarriage rates

• Increased breast cancer (estrogen dependant)

DES daughters

• Vaginal / cervical cancer

• 2x likely for breast cancer

• Reproductive structure abnormalities

• Infertility

• Ectopic pregnancy

• Miscarriage, stillbirth, preterm labor

• Endometriosis

• Uterine fibroids

DES sons

• Epididymal cysts

• Cryptorchidism (small or undescended testes)

• Microphallus

• Infertility

DES grandchildren

• Girls: Delayed menstruation regularity

• Boys: Hypospadias (higher rate of urethral opening in the wrong place)

Atrazine

• Widest used pesticides in the US

• Causes reproductive deformities in frogs

• Approved in drinking water at 3 ppb but causes deformities at 0.1 ppb

Lake Apopka Alligators

• Lake is a EPA superfund site, full of purely toxic stuff and dead animals

• Male alligators show up with reproductive problems like abnormally small penises

• Thought it was environmental estrogens but the chemicals are anti androgens (demasculinized, not feminized)

General sexual disruption in fish

• Rivers and estuaries are used for enormous amounts of industrial and domestic waste containing chemicals

• Birth control pills » hormones pass straight through and end up in urine and feces

• Lakes with untreated sewage had a large proportion of intersex fish

DDT - Pesticides

• An insecticide that can bind estrogen receptors

• Causes egg shell thinning in birds, very popular to control mosquitoes