Unit 9 Lectures





Chemical Signals
Animal Reproduction
Animal Development
Nervous System
Motor Mechanisms
Regulatory systems





Hormone~ chemical signal secreted
into body fluids (blood)
communicating regulatory messages
Target cells~ body cells that respond
to hormones
Endocrine system/glands~ hormone
secreting system/glands (ductless);
exocrine glands secrete chemicals
(sweat, mucus, enzymes) through
ducts
Neurosecretory cells~ actual cells
that secrete hormones
Feedback mechanisms ~ negative
and positive
Local regulators: cells adjacent to or near point of
secretion



Growth factors ~
proteins for cell proliferation
Nitric oxide (NO) ~
neurotransmitter; cell destruction; vessel
dilation
Prostaglandins ~
modified fatty acids secreted by placenta and
immune system; also found in semen


Mode of Action: Chemical
Signaling
1- Plasma membrane reception
• signal-transduction pathways (neurotransmitters, growth factors, most
hormones)
2- Cell nucleus reception
• steroid hormones, thyroid hormones, some local regulators
Vertebrate Endocrine System










Tropic hormones ~
a hormone that has another
endocrine gland as a target
Hypothalamus~pituitary
Pituitary gland
Pineal gland
Thyroid gland
Parathyroid glands
Thymus
Adrenal glands
Pancreas
Gonads (ovary, testis)










The hypothalamus & pituitary,
I
Releasing and inhibiting
hormones
Anterior pituitary:
Growth (GH)~bones
√gigantism/dwarfism
√acromegaly
Prolactin (PRL)~mammary glands;
milk production
Follicle-stimulating (FSH) &
Luteinizing (LH)~ovaries/testes
Thyroid-stimulating (TSH)~
thyroid
Adrenocorticotropic (ACTH)~
adrenal cortex
Melanocyte-stimulating (MSH)
Endorphins~natural ‘opiates’;
brain
pain receptors
The pituitary, II


The posterior
pituitary:
Oxytocin~
uterine and mammary gland
cell contraction

Antidiuretic (ADH)~
retention of water by
kidneys
The pineal, thyroid, & parathyroid

Melatonin~ pineal
gland; biological rhythms

Thyroid
hormones:
Calcitonin~
lowers blood calcium
Thyroxine~
metabolic processes

Parathyroid
(PTH)~ raises blood
calcium
The pancreas


Islets of Langerhans
Alpha cells:
•glucagon~ raises blood glucose
levels

Beta cells:
•insulin~ lowers blood glucose
levels

Type I diabetes
mellitus (insulin-dependent;
autoimmune disorder)

Type II diabetes
mellitus (non-insulin-
dependent; reduced responsiveness
in insulin targets)
The adrenal glands

Adrenal medulla (catecholamines): •epinephrine &
norepinephrine~
increase basal metabolic rate (blood glucose and
pressure)

Adrenal cortex (corticosteroids):
•glucocorticoids
(cortisol)~ raise blood glucose •mineralocorticoids (aldosterone)~
reabsorption of Na+ and K+
The gonads

Steroid hormones:
precursor is cholesterol

androgens
(testosterone)~ sperm
formation; male secondary sex
characteristics; gonadotropin

estrogens
(estradiol)~uterine lining
growth; female secondary sex
characteristics; gonadotropin

progestins
(progesterone)~uterine
lining growth
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.

Asexual

fission



Two individuals of
approximately equal size
(corals)
Creation of colonies
gemmules


(one parent)
(parent separation)
budding

Overview
(porifera)
Specialized groups of cells
fragmentation &
regeneration
(inverts)
 Body breaks into pieces
which develop into adults
Reproductive cycles

Parthenogenesis
unfertilized egg development;
haploid, sterile adults (honeybees)

Hermaphroditism
both male & female reproductive
systems; sessile & burrowing
organisms (earthworms)

Sequential
hermaphroditism
reversal of
gender during lifetime
•protogynous (female 1st)
•protandrous (male 1st)
Overview

Sexual
(fusion of haploid
gametes)




gametes
(sex cells)
zygote (fertilized egg)
ovum (unfertilized egg)
spermatozoon (male
gamete)
Mechanisms of sexual reproduction

Fertilization
(union of sperm and egg)

• external
• internal
Pheromones
chemical signals that influence the
behavior of others (mate
attractants)
Mammalian reproduction, I



The Human Male
Testes~ male gonads
Seminiferous tubules~
sperm formation

Leydig cells~ hormone
production


Scrotum~ outside body temp.
Epididymis~ sperm
development

Vas deferens~ sperm
propulsion


Seminal vesicles~ semen
Prostate gland~
anticoagulant; nutrients

Bulbourethral glands~
acid neutralizer

Penis/urethra~ semen
Spermatogenesis


Puberty until death!
Seminiferous tubules~
location


Primordial germ cell
(2N)~ differentiate into….
Spermatogonium (2N)~
sperm precursor






Repeated mitosis into….
Primary spermatocyte
(2N)
1st meiotic division
Secondary spermatocyte
(1N)
2nd meiotic division
Spermatids (1N)~Sertoli
cells….
Mammalian reproduction, II




The Human Female
Ovaries~ female gonads
Follicle~ egg capsule
Corpus luteum~ hormone
secretion


Oviduct~ fertilization
Uterus/endometrium~
womb/lining

Cervix/vagina~ sperm
receptacle
Oogenesis










As embryo until
menopause...
Ovaries
Primordial germ cells
(2N)
Oogonium (2N)
Primary oocyte (2N)
Between birth & puberty;
prophase I of meiosis
Puberty; FSH (Follicle
stimulating hormone);
completes meiosis I
Secondary oocyte (1N);
polar body
Meiosis II; stimulated by
fertilization
Ovum (1N); 2nd polar
body
The female pattern

Estrous cycles/estrus (many
mammals)

Menstrual cycle (humans and
many other primates):

Ovarian/Menstrual cycles~
•follicular phase~follicle
growth •ovulation~ oocyte
release •luteal phase~
hormone release
Embryonic & fetal development



Gestation ~ pregnancy
1st trimester:
Organogenesis


HCG hormone
(human
chorionic gonadotropin)


Development of body organs
menstruation override; pregnancy
test detection
Fetus

(week 8; all adult features)

Week 12, about 5 cm long
2nd Trimester

Fetus




About 30 cm and is active
Movement occurs
Visible growth in mother
Hormones are now
secreted by the
placenta, maintaining
pregnancy
3rd Trimester

Fetus



Grows to 3-3.5 kg and 50 cm
long (about 6-8lbs and 30 in)
Parturition ~birth
Labor ~uterine
contractions


Stimulated by positive feedback
of oxytoxin and prostaglansins
Lactation
~prolactin &
oxytocin generate production of
milk in the breast

Unique to mammals







Embryonic
development/fertilization
Preformation~ until 18th century; miniature infant in sperm or egg
At fertilization/conception:
Acrosomal reaction~ hydrolytic enzyme action on egg jelly coat….
Fast block to polyspermy~ membrane depolarization prevents multiple
fertilizations….
Cortical reaction~ release of calcium causes hardening of egg outer layer and
creates a...
Slow block to polyspermy and...
Egg activation~ increases metabolic activity; protein synthesis
The Fertilized Egg & Cleavage

Blastomeres~

Yolk~ nutrients stored in the
resultant
cells of cleavage/mitosis
egg

Vegetal pole~ side of egg
with high yolk concentration



Animal pole
~ side of egg
with low yolk concentration
Morula~solid ball of cells
Blastocoel~fluid-filled cavity
in morula

Blastula~hollow ball stage of
development
Gastrulation

Gastrula~ 2 layered, cup-shaped
embryonic stage



3 Embryonic germ layers:
Ectoderm~ outer layer; epidermis;
nervous system, etc.
Endoderm~ inner layer; digestive tract
and associated organs; respiratory, etc.

Mesoderm~skeletal; muscular; excretory,
etc.

Invagination~ gastrula buckling
process to create the...


Archenteron~ primitive gut
Blastopore~ open end of
archenteron
Organogenesis: organ formation

Blastodisc~ cap of cells on
top of yolk

Primitive streak~
invagination of blastodisc

Neural tube~ beginning of
spinal cord

Somites~

Neural crest~ bones and
vertebrae and
skeletal muscles
muscles of skull
Amniote embryos

Extraembryonic
membranes: •yolk sac
(support; circulatory function)
•amnion
(fluid-filled sac; protection)
•chorion
(placenta
formation)
•allantois
(nitrogenous waste)
Contraception





Contraception prevents sexual reproduction
Abstinence – both viable sperm and oocytes
are produced but cannot combine
Birth Control Pills/Patch/etc. – viable oocytes
are not released; prevention of release
Vasectomy – prevents sperm from being
released
Tubal ligation – prevents the oviduct from
capturing the egg and transporting to the
uterus
Contraception



Spermicides, diaphragms, cervical caps, etc –
prevent transportation of egg or sperm through
the female reproductive tract.
Intrauterine devices – prevent implantation of
blastocyst
Surgical abortion, abortion pill (RU-486) –
termination of pregnancy

RU-486 blocks progesterone receptors in the uterus, preventing the
maintenance of pregnancy
Miscarriage


Spontaneous abortion
Occurs in as many as 1/3 of all pregnancies


Often before the woman knows she is pregnant
Maintenance of pregnancy cannot be achieved:



Progesterone receptors are blocked
HCG production stops
Lutenizing hormone changes levels of progesterone
Modern Technology


Ability to detect genetic defects
Fertility treatments


In vitro fertilization
Experimental birth control for both men and
women targeting release of oocytes and
spermagenisis
Nervous System


Central Nervous System: brain, spinal cord;
the major pathways that information travels
on in the nervous system.
Peripheral Nervous System: nerves that
connect the actual muscle tissue and other
parts of the animal to the central nervous
system
Nervous systems

Effector cells~
muscle or
gland cells


Nerves~
bundles of neurons
wrapped in connective tissue
Central nervous
system (CNS)~ brain and
spinal cord

Peripheral nervous
system (PNS)~ sensory
and motor neurons
Structural Unit of Nervous System








Neuron~ structural and functional unit
Cell body~ nucelus and organelles
Dendrites~ impulses from tips to neuron
Axons~ impulses toward tips
Myelin sheath~ supporting, insulating layer
Schwann cells~PNS support cells
Synaptic terminals~ neurotransmitter releaser
Synapse~ neuron junction
Simple Nerve Circuit






Sensory neuron: convey information to
spinal cord
Interneurons: information integration
Motor neurons: convey signals to
effector cell (muscle or gland)
Reflex: simple response; sensory to
motor neurons
Ganglion (ganglia): cluster of nerve cell
bodies in the PNS
Supporting cells/glia: nonconductiong
cell that provides support, insulation,
and protection
Neural signaling, I

Membrane potential (voltage differences across the plasma
membrane)



Intracellular/extracellular ionic concentration difference
K+ diffuses out (Na+ in); large anions cannot
follow….selective permeability of the plasma membrane
Net negative charge of about -70mV
Sodium-Potassium Pumps

Controlled by gated ion channels





Expand/stretch in response to ligand binding or
change in membrane potential
[Na+] higher in the extracellular fluid
[K+] higher in cytosol
No signal = open K+ channels; passive
diffusion
Produces a resting potential
Action Potential




Brief, complete depolarization of the
membrane potential
Signal transduction opens the voltage
gated Na+ channels allowing Na+ to enter
the cell generating a positive cell value
Once the signal passes, the Na+ channels
close and prevent Na+ ions from entering
the cell
When the Na+ channels close, K+
channels open
Neural signaling, II






Excitable cells~ cells that can change membrane potentials (neurons, muscle)
Resting potential~ the unexcited state of excitable cells
Gated ion channels (open/close response to stimuli): photoreceptors; vibrations in
air (sound receptors); chemical (neurotransmitters) & voltage (membrane potential
changes)
Graded Potentials (depend on strength of stimulus):
1- Hyperpolarization (outflow of K+); increase in electrical gradient; cell becomes
more negative
2- Depolarization (inflow of Na+); reduction in electrical gradient; cell becomes less
negative
Neural signaling, III









Threshold potential: if stimulus reaches a
certain voltage (-50 to -55 mV)….
The action potential is triggered….
Voltage-gated ion channels (Na+; K+)
1-Resting state
•both channels
closed
2-Threshold •a stimulus opens some Na+
channels
3-Depolarization •action potential
generated •Na+ channels open; cell
becomes positive (K+ channels closed)
4-Repolarization •Na+ channels close,
K+ channels open; K+ leaves •cell
becomes negative
5-Undershoot •both gates close, but K+
channel is slow; resting state restored
Refractory period~ insensitive to
depolarization due to closing of Na+
gates
Neural signaling, IV






“Travel” of the action potential is self-propagating
Regeneration of “new” action potentials only after refractory period
Forward direction only
Action potential speed:
1-Axon diameter (larger = faster; 100m/sec)
2-Nodes of Ranvier (concentration of ion channels); saltatory conduction;
150m/sec
Synaptic communication






Presynaptic cell: transmitting cell
Postsynaptic cell: receiving cell
Synaptic cleft: separation gap
Synaptic vesicles:
neurotransmitter releasers
Ca+ influx: caused by action
potential; vesicles fuse with
presynaptic membrane and
release….
Neurotransmitter
Neurotransmitters




Acetylcholine (most common)
•skeletal muscle
Biogenic amines (derived from amino acids)
•norepinephrine
•dopamine
•serotonin
Amino acids
Neuropeptides (short chains of amino acids)
•endorphin
Vertebrate PNS




Cranial nerves (brain origin)
Spinal nerves (spine origin)
Sensory division
Motor division
•somatic system
voluntary, conscious control
•autonomic system
√parasympathetic
conservation of energy
√sympathetic
energy consumption
increase
The Vertebrate Brain

Forebrain
•cerebrum~memory, learning,
emotion
•cerebral cortex~sensory
and motor nerve cell bodies
•corpus
callosum~connects left and right
hemispheres
•thalamus; hypothalamus


Midbrain
•inferior (auditory) and superior
(visual) colliculi
Hindbrain
•cerebellum~coordination of movement
•medulla oblongata/ pons~autonomic,
homeostatic functions
Nerve Development & Stem Cells

Axons grow through a process of guidance



Signal molecules direct growth through the
binding of receptors
Receptors bind to the growth core
Adult human brains contain stem cells

These cells can differentiate into mature neurons
Neural Diseases & Disorders




Schizophrenia: hallucinations, delusions,
blunted emotions
Depression (includes bi-polar): manic (high
mood), and depressive (low mood)
behaviors
Alzheimer’s: age related dementia from
tangling of neurons and senile plaques
Parkinson’s: affects motor skills &
movement caused by death of
neurotransmitters and receptors
Memory Processing



Specific sensory input goes to the brain and
is integrated with various other sensory
areas
Left Hemisphere: specialized for high-speed
information processing involving speech and
logic operations.
Right Hemisphere: specialized for pattern
recognition, nonverbal ideation and
emotional processing
Learning Memory


Short term memory: Frontal lobes
Long Term Memory: Hippocampus and
amygdala



Brain decides what it important and what is not;
takes about 7 seconds
Once it is important, the hippocampus transfers it
to the amygdala where it becomes permanent
Permanent memories are filled using similar
memories as categories
Learning Memory

Best ways to force your brain to remember
something:


Make it a rhyme/song
Make flash cards and review them several times
Consciousness


Occurs in the cortex
The degree of consciousness is based upon
activity of the brain



From Brain Imaging Research
Offers an increasing picture of how neural
activity relates to conscious experiences
New and Developing area of research!
Emotions


Limbic system: mediates primary emotions
and attaches “feelings” to survival-related
functions
Neocortex: association with different emotions
during various phases of human development
Vertebrate Skeletal Muscle

Contract/relax:
antagonistic pairs w/skeleton


Muscles: bundle of….
Muscle fibers: single cell w/ many
nuclei consisting of….

Myofibrils: longitudinal bundles
composed of….

Myofilaments:
•Thin~ 2 strands of actin protein and a
regulatory protein
•Thick~ myosin protein

Sarcomere: repeating unit of muscle
tissue, composed of….




Z lines~sarcomere border
I band~only actin protein
A band~actin & myosin protein overlap
H zone~central sarcomere; only myosin
Sliding-filament model




Theory of muscle contraction
Sarcomere length reduced
Z line length becomes shorter
Actin and myosin slide past each other (overlap increases)
Actin-myosin interaction


1- Myosin head hydrolyzes ATP to ADP and inorganic phosphate (Pi);
termed the “high energy configuration”
2- Myosin head binds to actin; termed a “cross bridge”
Actin-myosin interaction



3- Releasing ADP and (Pi), myosin relaxes sliding actin; “low
energy configuration”
4- Binding of new ATP releases myosin head
Creatine phosphate~ supplier of phosphate to ADP
Muscle contraction regulation, I

Relaxation:

Contraction:
tropomyosin
blocks myosin binding sites on
actin
calcium
binds to toponin complex;
tropomyosin changes shape,
exposing myosin binding sites
Muscle contraction regulation, II

Calcium (Ca+)~
concentration regulated by
the….

Sarcoplasmic reticulum~
a specialized endoplasmic
reticulum


Stimulated by action
potential in a motor
neuron
T (transverse) tubules~
travel channels in plasma
membrane for action potential

Ca+ then binds to troponin
Sensory Organs


Transmission: energy is transduced into
potential, and conducted through impulses in
the CNS
Amplification: will increase the weak signal
from a sense organ for the brain to recognize
it


Noise it amplified more than 20 times before
reaching the inner ear
Integration: the processing of information
through sensory adaptation, receptor
transduction, etc
Sensory Receptors



Pain receptors: dendrites in the epidermis
that respond to various stimulus
Thermoreceptors: respond to heat or cold;
regulate body temperature
Chemoreceptors: receptors that target
chemicals, two classes


general receptors transmit information about
solute concentration
Specific receptors transmit information about
taste, smell, etc.
Sensory organs



The ear – the ear is used in hearing and
amplifies sound to send signals to the
brain
The eye – uses light to see; vertebrates
have a single lens that allows detection
of color and shape through rods and
cones
The mouth – used in chemoreception of
taste and smell; usually taste and smell
are interrelated.