April 22, 2014 – Hearing and equilibrium II

1. Review of the mechanics of hearing.2. Maintaining equilibrium in mammals.3. Equilibrium in other animals 4. Sensory deprivation and hallucinations. 5. Cell-to-cell signalling – Hormones!!!

Detects sound frequency transmits signal to the auditory nerve

Vestibular canal

Tympaniccanal

Cochlear duct

Tectorialmembrane

Hair cells

Axons of sensoryneurons

• 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 (height of

wave)

Hearing- Mammals (con’t)

2. Pitch- Frequency (no. of waves per unit time)

1. Amplitudelarger 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

Hearing- Mammals (con’t)

Equilibrium

balance and body position/orientation

Equilibrium- Mammals

Semicircular Canals

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

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

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.)

Equilibrium- Mammals

Semicircular Canals

Equilibrium- Aquatic OrganismsLateral 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

Lateral Line SystemWater 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- Lateral Line (con’t)

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

Equilibrium- Invertebrates

2. Pathway: a. Gravity causes statoliths to settle downwardb. Once reach bottom of chamber, stimulating cilia of receptor

cellsc. 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 categoriesEndocrine cells may be organized into glands

Neurotransmitters

Introduction to chemical signals in animals – Major categories

Neuroendocrine pathway

Neuroendocrinesignal

Endocrine pathway Neuroendocrine-to-endocrine pathway

Neuroendocrinesignal

Endocrinesignal

Endocrinesignal

Endocrine cell

Effectorcell

Response

Response

Stimulus Stimulus

Feed

back

inhi

bitio

n

Feed

back

inhi

bitio

n Sensor cell

Effectorcell

Feed

back

inhi

bitio

n

Neural signal

CNS

Stimulus

Sensor cell

Neural signal

CNS

Response

Effectorcell

Endocrine cell

Endocrine systems are regulated by negative feedback

Figure 47-3-1Hypothalamus

Growth-hormone-releasing hormone:stimulates release of GH from pituitarygland

Corticotropin-releasing hormone (CRH):stimulates release of ACTH from pituitarygland

Gonadotropin-releasing hormone:stimulates release of FSH and LH from pituitary gland

Thyroid-releasing hormone: stimulatesrelease of TSH from thyroid gland

Antidiuretic hormone (ADH): promotesreabsorption of H2O by kidneys

Oxytocin: induces labor and milk releasefrom mammary glands in females

Steroids

PolypeptidesAmino acid derivatives

Figure 47-3-2

Adrenal glands

Thyroid gland

Thyroxine: increases metabolic rateand heart rate; promotes growth

Kidneys

Epinephrine: produces many effectsrelated to short-term stress response

Aldosterone: increases reabsorption ofNa+ by kidneys

Cortisol: produces many effects related toshort-term and long-term stress responses

Vitamin D: decreases blood Ca2+

Testes (in males)

Erythropoietin (EPO): increasessynthesis of red blood cells

Testosterone: regulates developmentand maintenance of secondary sexcharacteristics in males; other effects

Steroids

PolypeptidesAmino acid derivatives

Figure 47-3-3

Pituitary gland

Thyroid-stimulating hormone (TSH):stimulates thyroid gland to secretethyroxine

Prolactin: stimulates mammary glandgrowth and milk production in females

Follicle-stimulating hormone (FSH)and luteinizing hormone (LH): involvedin production of sex hormones;regulate menstrual cycle in females

Growth hormone (GH): stimulates growth

Adrenocorticotropic hormone (ACTH):stimulates adrenal glands to secreteglucocorticoids

Steroids

PolypeptidesAmino acid derivatives

Figure 47-3-4

Parathyroid glands

Pancreas (islets of Langerhans)

Ovaries (in females)

Insulin: decreases blood glucose

Glucagon: increases blood glucose

Estradiol: regulates development andmaintenance of secondary sexcharacteristics in females; other effectsProgesterone: prepares uterus for pregnancy

Parathyroid hormone (PTH): increases blood Ca2+

Steroids

PolypeptidesAmino acid derivatives

Steroids

CortisolEpinephrine

Amino AcidDerivatives

Receptor

Secretin

Peptides and Polypeptides

Receptor

Receptor

Target cell

Most not lipid soluble;bind to receptors onsurface of target cell

Not lipid soluble;bind to receptors onsurface of target cell

Lipid soluble;bind to receptorsinside target cell

Chemical characteristics of hormones – major classes

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 transductionpathway. This can affect the properties of enzymes/proteins, etc. or it may affect gene expression.

This picture shows a hormone traveling throughthe cell membrane and binding with a transcription factor.

Which of the following statements are true?

A) This is a membrane soluble (hydrophobic) hormone thatalters gene transcription.

B) This is a membrane soluble (hydrophobic) hormone thatalters immediate enzyme activity and cell processes.

C) This is a membrane insoluble (hydrophilic) hormone thatalters gene transcription.

D) This is a membrane insoluble (hydrophilic) hormone thatalters 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. The hormone was membrane insoluble.B. The hormone was membrane soluble.C. The hormone initiated a signal transduction pathway.D. A and C