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April 22, 2014 – Hearing and equilibrium II
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Review of the mechanics of hearing.
Maintaining equilibrium in mammals.
Equilibrium in other animals
Sensory deprivation and hallucinations.
Cell-to-cell signalling – Hormones!!!
Detects sound frequency
transmits signal to the auditory
nerve
Vestibular
canal
Cochlear
duct
Tectorial
membrane
Hair cells
Axons of sensory
neurons
Tympanic
canal
Hearing- Mammals (con’t)
• Two Components of Sound Wave:
There are two main components of the sound wave
that are detected and used by the auditory system:
1. Volume- Amplitude
wave)
(height of
2. Pitch- Frequency
(no. of waves per unit time)
Hearing- Mammals (con’t)
1. Amplitude
larger amplitude= louder sound
-larger amplitude results in stronger pressure on the
hair cells, thereby causing more action potentials
(more neurotransmitters released)
2. Pitch
- basilar membrane varies in thickness and flexibility
-base= narrow and stiff; stimulated by higher pitch
-tip (apex)= wider and more flexible; stimulated by lower
pitch
Equilibrium
balance and body position/orientation
Equilibrium- Mammals
Organs to detect body position and
maintain balance located in inner ear
1.) Utricle and Saccule (2 parts of same
organ)
-located next to oval window
-detect which direction is up and
detect body position and acceleration
2.) Semicircular Canals (3 canals in
total)
-next to utricle
-detect angular movements
Semicircular Canals
1. Utricle and saccule contain clusters of hair cells embedded in a
gel called a cupula.
2. Cupula contains otoliths.
3. Cupula (with otoliths) is heavier than the endolymph (fluid) in the
utricle and saccule, so gravity is pulling the cupula down on to the
hairs of the hair cells.
4. Changes in angle of body (i.e. changes in position of head)
change the force on the hair cells.
- causes stimulation of some cells that weren’t stimulated before
- causes some to increase/decrease their signals
Equilibrium- Mammals
Semicircular Canals
3 canals (“loops”) - one for each plane:
- side-to-side
- front and back
- up and down
Same mechanism of stimulation as for
utricle and saccule (cupula with
otoliths, hair cells, etc.)
Semicircular Canals
Equilibrium- Aquatic Organisms
Lateral Line System
1. Fish: lateral line on both sides of body
series of mechanoreceptors called neuromasts on body just under
the epidermis
Small openings (pores) in epidermis allow for water to enter into
lateral line canals
Equilibrium- Lateral Line (con’t)
Lateral Line System
Water stimulates clusters of hair cells in the neuromasts by bending the
cupula (gelatinous cap over the hair cells)
Stimulation causes release of neurotransmitters, sending signals through
sensory nerves to brain
Equilibrium- Invertebrates
Most invertebrates have sensory “organ”
called statocysts
Parts of statocyst:
-layer of ciliated receptor cells surrounding
an open chamber
-inside chamber are grains of dense
material called statoliths
2. Pathway:
a. Gravity causes statoliths to settle downward
b. Once reach bottom of chamber, stimulating cilia of receptor cells
c. Stimulated cells release neurotransmitters, stimulating
connecting sensory nerve fibers
Sensory deprivation and hallucination
• Degradation of vision and hearing is associated with
visual and auditory hallucinations.
• Thought to be associated with hyperactivity or visual
and auditory brain regions that received degraded
input from sensory organs.
• Distinctly different in character from drug-induced and
psychotic hallucinations
• Charles Bonnett syndrome.
• Link to Oliver Sacks’ TED talk.
Introduction to chemical signals in animals – Major categories
Endocrine
cells may be
organized
into glands
Autocrine signals
Paracrine signals
Endocrine signals
act on the same cell
that secretes them.
diffuse locally and act
on neighboring cells.
are hormones carried
between cells by blood
or other body fluids.
Introduction to chemical signals in animals – Major categories
Neurotransmitters
Neural signals
diffuse a short distance
between neurons.
Neuroendocrine signals
Pheromones
are released from neurons
but are carried by blood or
other body fluids and act
on distant cells.
are released into the
environment and act
on a different individual.
Endocrine systems are regulated by negative feedback
Endocrine pathway
Neuroendocrine pathway
Stimulus
Neuroendocrine-to-endocrine pathway
Stimulus
Stimulus
Endocrine cell
Endocrine
signal
Effector
cell
Response
Sensor cell
Sensor cell
Neural signal
Neural signal
CNS
CNS
Neuroendocrine
signal
Effector
cell
Response
Neuroendocrine
signal
Endocrine cell
Endocrine
signal
Effector
cell
Response
Figure 47-3-1
Hypothalamus
Growth-hormone-releasing hormone:
stimulates release of GH from pituitary
gland
Corticotropin-releasing hormone (CRH):
stimulates release of ACTH from pituitary
gland
Thyroid-releasing hormone: stimulates
release of TSH from thyroid gland
Gonadotropin-releasing hormone:
stimulates release of FSH and LH from
pituitary gland
Antidiuretic hormone (ADH): promotes
reabsorption of H2O by kidneys
Oxytocin: induces labor and milk release
from mammary glands in females
Polypeptides
Amino acid derivatives
Steroids
Figure 47-3-2
Polypeptides
Amino acid derivatives
Steroids
Thyroid gland
Thyroxine: increases metabolic rate
and heart rate; promotes growth
Adrenal glands
Epinephrine: produces many effects
related to short-term stress response
Cortisol: produces many effects related to
short-term and long-term stress responses
Aldosterone: increases reabsorption of
Na+ by kidneys
Kidneys
Erythropoietin (EPO): increases
synthesis of red blood cells
Vitamin D: decreases blood Ca2+
Testes (in males)
Testosterone: regulates development
and maintenance of secondary sex
characteristics in males; other effects
Figure 47-3-3
Polypeptides
Amino acid derivatives
Steroids
Pituitary gland
Growth hormone (GH): stimulates
growth
Adrenocorticotropic hormone (ACTH):
stimulates adrenal glands to secrete
glucocorticoids
Thyroid-stimulating hormone (TSH):
stimulates thyroid gland to secrete
thyroxine
Follicle-stimulating hormone (FSH)
and luteinizing hormone (LH): involved
in production of sex hormones;
regulate menstrual cycle in females
Prolactin: stimulates mammary gland
growth and milk production in females
Figure 47-3-4
Polypeptides
Amino acid derivatives
Steroids
Parathyroid glands
Parathyroid hormone (PTH):
increases blood Ca2+
Pancreas (islets of Langerhans)
Insulin: decreases blood glucose
Glucagon: increases blood glucose
Ovaries (in females)
Estradiol: regulates development and
maintenance of secondary sex
characteristics in females; other effects
Progesterone: prepares uterus for
pregnancy
Chemical characteristics of hormones – major classes
Peptides and Polypeptides
Secretin
Amino Acid
Derivatives
Steroids
Cortisol
Epinephrine
Receptor
Receptor
Not lipid soluble;
bind to receptors on
surface of target cell
Target cell
Most not lipid soluble;
bind to receptors on
surface of target cell
Lipid soluble;
bind to receptors
inside target cell
Receptor
Hormone Transport and Action on Target
Hydrophobic messengers pass into
cell (and sometimes the nucleus)
where they bind with transcription
factors which affect gene
expression.
Hydrophilic hormones bind to a
receptor on the cell membrane
which causes several reactions
known as a signal transduction
pathway. This can affect the
properties of enzymes/proteins, etc.
or it may affect gene expression.
This picture shows a hormone traveling through
the cell membrane and binding with a transcription factor.
Which of the following statements are true?
A) This is a membrane soluble (hydrophobic) hormone that
alters gene transcription.
B) This is a membrane soluble (hydrophobic) hormone that
alters immediate enzyme activity and cell processes.
C) This is a membrane insoluble (hydrophilic) hormone that
alters gene transcription.
D) This is a membrane insoluble (hydrophilic) hormone that
alters immediate enzyme activity and cell processes.
Barry Bonds was accused of using a steriod ‘the cream’ to increase his athletic
performance. He supposedly applied this to his skin. What does this tell you about the
nature of this hormone?
A.
B.
C.
D.
The hormone was membrane insoluble.
The hormone was membrane soluble.
The hormone initiated a signal transduction pathway.
A and C