Chapter 4: Sex Differences in Behavior: Animal and Human Models Examining the Neural and...
-
date post
21-Dec-2015 -
Category
Documents
-
view
221 -
download
2
Transcript of Chapter 4: Sex Differences in Behavior: Animal and Human Models Examining the Neural and...
Chapter 4:
Sex Differences in Behavior: Animal and Human Models Examining the Neural and
Neuroendocrine aspects of the Brain.
4.2 Synapses may form either on dendritic spines or on the shaft of a dendrite
4.5 Cichlid fish show changes in neuronal cell size in response to social conditions
4.8 Singing in female songbirds falls along a broad continuum
Santiago Ramon Y. Cajal (1852-1934)Founding Scientist in the Modern Approach toNeuroscience. Received Nobel Prize in 1906
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.1: The nervous system’s functions, p. 388.
Sensory input
Motor output
Integration
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.2: Levels of organization in the nervous system, p. 389.
Central nervous system (CNS) Brain and spinal cord Integrative and control centers
Sensory (afferent) division Somatic and visceral sensory nerve fibers Conducts impulses from receptors to the CNS
Motor (efferent) division Motor nerve fibers Conducts impulses from the CNS to effectors (muscles and glands)
Autonomic nervous system (ANS) Visceral motor (involuntary) Conducts impulses from the CNS to cardiac muscles, smooth muscles, and glands
Sympathetic division Mobilizes body systems during activity
Parasympathetic division Conserves energy Promotes housekeeping functions during rest
Peripheral nervous system (PNS) Cranial nerves and spinal nerves Communication lines between the CNS and the rest of the body
Somatic nervous System Somatic motor (voluntary) Conducts impulses from the CNS to skeletal muscles
= Structure= Function
Key:
Centralnervoussystem(CNS)
= Sensory (afferent)division of PNS= Motor (efferent)division of PNS
Key: Brain
SpinalcordSkin
Visceral organ
Skeletalmuscle
Peripheral nervous system(PNS)
Motor fiber ofsomatic nervoussystem
Somatic sensoryfiber
Sympatheticmotor fiber of ANS
Parasympatheticmotor fiber of ANS
Visceralsensory fiber
(a)
(b)
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.3: Neuroglia, p. 390.
(a) Astrocyte
(d) Oligodendrocyte
(e) Sensory neuron with Schwann cells and satellite cells
(b) Microglial cell
(c) Ependymal cells
Schwann cells(forming myelin sheath)
Cell bodyof neuron
Satellite cells
Nerve fiber
Capillary
Neuron
Nerve fibers
Myelin sheath
Process ofoligodendrocyte
Fluid-filled cavity
Brain or spinal cord tissue
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.4: Structure of a motor neuron, p. 392.
(b)
(a)
Dendrites(receptiveregions)
Cell body(biosynthetic centerand receptive region)
Nucleolus
Nucleus
Terminal branches(telodendria)
Nissl bodies
Axon(impulse generatingand conductingregion)
Axon terminals(secretorycomponent)
Axon hillock
Neurilemma(sheath ofSchwann)
Node of Ranvier
Impulsedirection
Schwann cell(one inter-node)
Neuron cell body
Dendriticspine
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.5: Relationship of Schwann cells to axons in the PNS, p. 394.
(a)
(b)
(c)
(d)
Schwann cellcytoplasm
Axon
NeurilemmaMyelinsheath
Schwann cellnucleus
Schwanncell plasmamembrane
Myelin sheath
Schwann cellcytoplasm
Neurilemma
Axon
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.6: Operation of gated channels, p. 398.
(a) Chemically gated ion channel
Na+
K+K+
Na+
(b) Voltage-gated ion channel
Na+
Na+
Receptor
Neurotransmitter chemical attached to receptor
Closed Open
Membranevoltagechanges
Closed Open
Chemicalbinds
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.7: Measuring membrane potential in neurons, p. 399.
Voltmeter
Microelectrodeinside cell
Plasmamembrane
Ground electrodeoutside cell
Neuron
Axon
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.8: The basis of the resting membrane potential, p. 399.
Na+Na+
K+K+
K+
K+
Na+
Na+
Na+
Na+
Cell interiorNa+
15 mMK+
150 mMCl–
10 mMA–
100 mMNa+
150 mMA–
0.2 mM
Cell exterior
K+
5 mMCl–
120 mM
Cellexterior
Cellinterior
Plasmamembrane
Na+–K+
pumpDif
fusi
on
K+ Na
+ Diffu
sion
-70 mV
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.9: Depolarization and hyperpolarization of the membrane, p. 400.
Depolarizing stimulus
Mem
bra
ne
po
ten
tial
(vo
ltag
e, m
V)
Time (ms)
0–100
–70
0
–50 –50
+50
1 2 3 4 5 6 7
Hyperpolarizing stimulus
Mem
bra
ne
po
ten
tial
(vo
ltag
e, m
V)
Time (ms)
0 1 2 3 4 5 6 7–100
–70
0
+50
Insidepositive
Insidenegative
(a) (b)
Restingpotential
DepolarizationRestingpotential
Hyper-polarization
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.10: The mechanism of a graded potential, p. 401.
(b)
Depolarized region Stimulus
Plasmamembrane
Depolarization Spread of depolarization(a)
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.11: Changes in membrane potential produced by a depolarizing graded potential, p. 402.
Distance (a few mm)
–70Resting potential
Active area(site of initialdepolarization)
Mem
bra
ne
po
ten
tial
(m
V)
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.12: Phases of the action potential and the role of voltage-gated ion channels, p. 403.
0 1 2 3 4–70–55
0
+30M
emb
ran
e p
ote
nti
al (
mV
)
Time (ms)
Rel
ativ
e m
emb
ran
e p
erm
eab
ilit
y
Na+Na+
K+K+
Outsidecell
Insidecell
Outsidecell
Insidecell
Depolarizing phase: Na+
channels openRepolarizing phase: Na+
channels inactivating, K+
channels openAction potential
PNaPK Threshold
Na+Na+
K+K+
Outside cell
Insidecell
Outsidecell
Insidecell
Inactivation gate
Activationgates
Potassiumchannel
Sodiumchannel
Resting state: All gated Na+
and K+ channels closed (Na+ activation gates closed; inactivation gates open)
Hyperpolarization: K+
channels remain open; Na+ channels resetting
2
2
3
4
4
1
11
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.13: Propagation of an action potential (AP), p. 405.
–70
+30
(a) Time = 0 ms (b) Time = 2 ms (c) Time = 4 ms
Voltageat 2 ms
Voltageat 4 ms
Voltageat 0 ms
Resting potential
Peak of action potential
Hyperpolarization
Me
mb
ran
e p
ote
nti
al
(mV
))
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.14: Relationship between stimulus strength and action potential frequency, p. 406.
Time (ms)
Vo
ltag
eM
emb
ran
e p
ote
nti
al (
mV
)
–70
0
+30
Threshold
Actionpotentials
Stimulusamplitude
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.15: Refractory periods in an AP, p. 406.
Stimulus
Mem
bra
ne
po
ten
tial
(m
V)
Time (ms)
–70
0
+30
0 1 2 3 4 5
Absolute refractoryperiod
Relative refractoryperiod
Depolarization(Na+ enters)
Repolarization(K+ leaves)
After-hyperpolarization
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.16: Saltatory conduction in a myelinated axon, p. 407.
Node of Ranvier
Cell bodyMyelinsheath
Distalaxon
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.17: Synapses, p. 409.
(a)
(b)
Cell body
Dendrites
Axon
Axodendriticsynapses
Axoaxonicsynapses
Axosomaticsynapses
Axosomaticsynapses
Soma of postsynaptic neuron
Axon
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.18: Events at a chemical synapse in response to depolarization, p. 410.
Synaptic vesiclescontaining neurotransmitter molecules
Axon of presynapticneuron
Synapticcleft
Ion channel(closed)
Ion channel (open)
Axon terminal of presynaptic neuron
Postsynapticmembrane
Mitochondrion
Ion channel closed
Ion channel open
Neurotransmitter
Receptor
Postsynapticmembrane
Degradedneurotransmitter
Na+
Na+
Ca2+
Action Potential
1
2
3 4
5
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.19: Postsynaptic potentials, p. 412.
Threshold
Me
mb
ran
e p
ote
nti
al
(mV
)
Time (ms)
+30
0
–70
–55
10 20
(a) Excitatory postsynaptic potential (EPSP)
Threshold
Me
mb
ran
e p
ote
nti
al
(mV
)
Time (ms)
+30
0
–70
–55
10 20
(b) Inhibitory postsynaptic potential (IPSP)
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.24: Types of circuits in neuronal pools, p. 422.
(a) Divergence in same pathway
(e) Reverberating circuit
(f) Parallel after-discharge circuit
(b) Divergence to multiple pathways
(c) Convergence, multiple sources
(d) Convergence, single source
Input Input
Output Output
Input
OutputInput
Output
Input 1
Input 2 Input 3
Output
OutputInput
Why Study Bird Song?
Bird song has been a classic behavioral response studied in animals to help us understand sexually dimorphic differences in brain organization.
By studying bird song and the neural and neuroendocrine basis of bird song, we can better understand the principles of how the brain organizes itself during development.
This information about bird song can then be used to understand and/or predict aspects of organization of the brain of other animals including in humans.
Major Regions of the Bird Brain Associated with Song:
HVC = higher vocal center
RA = robust nuclusu of the archistriatum
nXIIts = hypoglossal nerve
DM = dorsomedial region of the nucleus intercollicularis
ICo = intercollicularis
Syrinx = the vocal organ in birds that produces sound (equivalent to our larynx)
A typical bird syrinx.
4.9 The neural basis of bird song
Note that in birds with sexually dimorphic song abilities, these brain regions are typically much larger in males than in females of the species.
4.10 Singing in zebra finches is organized by estrogens but activated by androgens
4.11 The sonic organs are used by Type I male midshipman fish to attract females to their nests
The sonic organs are sound producing muscles attached to the swim bladder in these fish.
Type 1 males have well developed sonic organs (6x) compared to Type 2 males or females.
The Type 1 male is an aggressive male.
The Type 2 male has a “sneaker” reproductive behavior pattern and actually has roughly a 9x gonad:body mass ratio compared to Type 1 males.
4.12 Urination postures of domestic dogs
4.15 The frequency of rough-and-tumble and pursuit play (Part 1)
Study of Rhesus Monkeys The pseudohermaphrodites are females who received in utero exposure to exogenous androgens.
4.15 The frequency of rough-and-tumble and pursuit play (Part 2)
4.16 Contributions of activational and organizational effects of hormones to behavior
Known Brain Differences in Humans:
SDN-POA = sexually dimorphic nucleus of the preoptic area of the hypothalamus.
The volume of SDN in medial preoptic area is modified by hormones, among which testosterone is proved to be of much importance. The larger volume of male SDN is correlated to the higher concentration of fetal testosterone level in males than in females.
From Roger Gorski’s Lab at Yale University:
Coronal rat brain sections showing the SDN-POA
A: male; B: female; C: female treated perinatally with testosterone; D: female treated perinatally with the synthetic estrogen diethylstilbestrol.
INAH-3 = the third interstitial nucleus of the anterior hypothalamus
The INAH has been implicated in sexual behavior because of known sexual dimorphism in this area in humans and because it corresponds to an area of the hypothalamus that when lesioned, impairs heterosexual behavior in non-human primates without affecting sex drive.
It has been reported to be smaller on average in homosexual men than in heterosexual men, and in fact has approximately the same size as INAH 3 in heterosexual women.
The above information is based on Simon Levay’s work that was published in the journal Science in 1991.
LeVay S (1991). A difference in hypothalamic structure between homosexual and heterosexual men. Science, 253, 1034-1037.
4.17 Average sex differences in behavior often reflect significant overlap between the sexes
4.18 Congenital absence of the olfactory bulbs in Kallmann syndrome
Kallmann Syndrome - hypogonadism (decreased functioning of the glands that produce sex hormones) caused by a deficiency of gonadotropin-releasing hormone (GnRH) which is created by the hypothalamus.
Alternative names include:
hypothalamic hypogonadism
or
hypogonadotropic hypogonadism
Males with this condition have smaller than average testes, are infertile, and express anosmia (the inability to detect odors)
This is due to incomplete development of the olfactory bulb embryologically.
The lack of olfactory bulb development results in the lack of GnRH cell development (the cells in the olfactory bulb normally migrate during development to the hypothalamus
4.19 A possible sex difference in the corpus callosum
Corpus callosum - a structure of the mammalian brain in the longitudinal fissure that connects the left and right cerebral hemispheres. It facilitates communication between the two hemispheres.
This may explain certain sexually dimporphic right/left communication disorders are more prevelant in males than females….. such as ADHD, schizophrenia. This may also suggest why females may have greater verbal cognition and why some task performance skills are sexually dimorphic…
4.20 Performance on certain tasks favor one sex over the other
Females > Males Males > Females
Box 4.5 Hormones, Sex Differences, and Art (Part 1)
Box 4.5 Hormones, Sex Differences, and Art (Part 2)
Male
Male
Male
Female with CAH
Female with CAH
Female
Female
All drawings by children aged 5-7.
Congenital Adrenal Hyperplasia (CAH) - an autosomal recessive disease group resulting in mutations of genes for hormone production in the brain that guid the biochemical steps of production of cortisol from cholesterol by the adrenal glands (Corticotropin Releasing Hormone (CRH) or Corticotropin Inhibiting Hormone (CRIH)) CRIH is also sometimes called Atriopeptin.
Most of these conditions involve excessive or deficient production of sex steroids and can alter development of primary or secondary sex characteristics in some affected infants, children, or adults.