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3. Receptors
• Rods – sense low levels of light
• Cones – sense higher level blue, green & red light
Fig. 10.36
3. Receptors
• Rods – sense low levels of light
• Cones – sense higher level blue, green & red light
Fig. 10.40
3. Receptors
• Rods – sense low levels of light
• Cones – sense higher level blue, green & red light
C. Receptor transduction
1. Rhodopsin
Fig. 10.36
3. Receptors
• Rods – sense low levels of light
• Cones – sense higher level blue, green & red light
C. Receptor transduction
1. Rhodopsin
• Retinene (photopigment) + opsin (protein)
2. Light
• Retinene – cis  trans configuration
Fig. 10.37
C. Receptor transduction
1. Rhodopsin
• Retinene (photopigment) + opsin (protein)
2. Light
• Retinene – cis  trans configuration
Fig. 10.37
C. Receptor transduction
1. Rhodopsin
• Retinene (photopigment) + opsin (protein)
2. Light
• Retinene – cis  trans configuration
3. trans Retinene
• Activates g-protein (transducin) cascade
• Closes Na+ channels
• Hyperpolarizes cell
Fig. 10.37
3. trans Retinene
• Activates g-protein (transducin) cascade
• Closes Na+ channels
• Hyperpolarizes cell
Fig. 10.37
3. trans Retinene
• Activates g-protein (transducin) cascade
• Closes Na+ channels
• Hyperpolarizes cell
D. Dark vs. light
1. Dark
• Photoreceptors depolarized and inhibitory
• Inhibit adjacent cells in retina
D. Dark vs. light
1. Dark
• Photoreceptors depolarized and inhibitory
• Inhibit adjacent cells in retina
2. Light
Fig. 10.39
1. Dark
• Photoreceptors inhibitory and depolarized
• Inhibit adjacent cells in retina
2. Light
• Receptors hyperpolarized (inhibited)
Fig. 10.39
1. Dark
• Photoreceptors inhibitory and depolarized
• Inhibit adjacent cells in retina
2. Light
• Receptors hyperpolarized (inhibited)
• Light is sensed
E. Dark adaptation
1. Light
• Receptors “bleached”
•  rhodopsin in receptors
2. Dark
• 1st 5 minutes –  rhodopsin in cones
• ~ 20 minutes – max sensitivity
E. Dark adaptation
1. Light
• Receptors “bleached”
•  rhodopsin in receptors
2. Dark
• 1st 5 minutes –  rhodopsin in cones
• ~ 20 minutes – max. sensitivity
• Due to  rhodopsin in rods
• Light sensitivity  by 100,000x
Chapter 11 – Endocrine
Endocrine glands – secrete into blood
Chapter 11 – Endocrine
Endocrine glands – secrete into blood
I. General info.
A. Classifications
Fig. 11.1
Chapter 11 – Endocrine
Endocrine glands – secrete into blood
I. General info.
A. Classifications
1. Amines – derived from single amino acids
Fig. 11.3
• Thyroid hormone
• Epinephrine
Fig. 9.9
I. General info.
A. Classifications
1. Amines – derived from single amino acids
• Thyroid hormone
• Epinephrine
2. Polypeptides – chains of amino acids
• Antidiuretic hormone
• Insulin
disulfide bridges
I. General info.
A. Classifications
1. Amines – derived from single amino acids
• Thyroid hormone
• Epinephrine
2. Polypeptides – chains of amino acids
• Antidiuretic hormone
• Insulin
3. Glycoproteins – carbohydrate + amino acids chains
• Follicle stimulating hormone (FSH)
• Luteinizing hormone (LH)
4. Steroids – based on cholesterol (lipid)
3. Glycoproteins – carbohydrate + amino acids chains
• Follicle stimulating hormone (FSH)
• Luteinizing hormone (LH)
4. Steroids – based on cholesterol (lipid)
• Progesterone
• Testosterone
• Cortisol
Fig. 11.2
3. Glycoproteins – carbohydrate + amino acids chains
• Follicle stimulating hormone (FSH)
• Luteinizing hormone (LH)
4. Steroids – based on cholesterol (lipid)
• Progesterone
• Testosterone
• Cortisol
B. Pre- vs. Prohormones
1. Prohormones
• Peptide contained in longer peptide (e.g. opioids)
B. Pre- vs. Prohormones
1. Prohormones
• Peptide contained in longer peptide (e.g. opioids)
• Unessential peptide portions cleaved
• True of all peptide hormones
B. Pre- vs. Prohormones
1. Prohormones
• Peptide contained in longer peptide (e.g. opioids)
• Unessential peptide portions cleaved
• True of all peptide hormones
2. Prehormones
• Single molecule (e.g. thyroid hormone)
• Inactive until changed by target cell
Fig. 11.3
B. Pre- vs. Prohormones
1. Prohormones
• Peptide contained in longer peptide (e.g. opioids)
• Unessential peptide portions cleaved
• True of all peptide hormones
2. Prehormones
• Single molecule (e.g. thyroid hormone)
• Inactive until changed by target cell
C. Hormone common aspects
• Blood born
• Receptors on/in target cells
•
Specific effect on target cell
C. Hormone common aspects
• Blood born
• Receptors on/in target cells
• Specific effect on target cell
• Can be turned off
D. Interactions
1. Synergistic
•
•
Additive or complementary
e.g. – epinephrine & norepi. on heart
2. Permissive
D. Interactions
1. Synergistic
• Additive or complementary
• e.g. – epinephrine & norepi. on heart
2. Permissive
• Hormone increases responsiveness of different
hormone
•
e.g. – cortisol allows epi. & norepi. to have
catabolic effects
3. Priming effect
• Hormone presence increases sensitivity/effect of
same hormone
2. Permissive
•
Hormone increases responsiveness of different
hormone
•
e.g. – cortisol allows epi. & norepi. to have
catabolic effects
3. Priming effect
• Hormone presence increases sensitivity/effect of
same hormone
•
e.g. – GnRH causes AP to be more sensitive to
GnRH
4. Antagonistic
• Opposite effects
3. Priming effect
•
Hormone presence increases sensitivity/effect of
same hormone
•
e.g. – GnRH causes AP to be more sensitive to
GnRH
4. Antagonistic
• Opposite effects
• e.g. – Insulin ( glucose stores) & glucagon (
glucose stores)
E. Hormone levels
1. Half-life
• Time for metabolic clearance of half of hormone
E. Hormone levels
1. Half-life
• Time for metabolic clearance of half of hormone
2. Physiological levels
•
Normal levels
3. Pharmacological levels
• Abnormally high levels
• Different physiological effects
4. Downregulation/desensitization
• Prolonged exposure
•  sensitivity of target tissue
4. Downregulation/desensitization
•
•
Prolonged exposure
 sensitivity of target tissue
II. Hormone mechanisms
A. Steroid hormones
1. Transport
• On carrier protein in blood
II. Hormone mechanisms
A. Steroid hormones
1. Transport
• On carrier protein in blood
•
Passive diffusion through membrane
Fig. 11.4
A. Steroid hormones
1. Transport
• On carrier protein in blood
• Passive diffusion through membrane
• Binds receptor in cytoplasm
2. Receptor
• Ligand binding domain – binds steroid
• DNA binding domain – binds DNA
3. Receptor-ligand complex
Fig. 11.5
2. Receptor
•
•
Ligand binding domain – binds steroid
DNA binding domain – binds DNA
3. Receptor-ligand complex
•
•
Translocates to nucleus
Two complexes bind two
receptor half sites on
DNA (dimerization)
Fig. 11.5
Fig. 11.4
3. Receptor-ligand complex
•
•
Translocates to nucleus
Two complexes bind two receptor half sites on
DNA (dimerization)
•
•
Form homodimer
Activate transcription
Fig. 11.5
Fig. 11.4
3. Receptor-ligand complex
•
•
Translocates to nucleus
Two complexes bind two receptor half sites on
DNA (dimerization)
•
•
Form homodimer
Activate transcription
4. On DNA
• Hormone response
element recognized
by complex
Fig. 11.5
•
Form homodimer
•
Activate transcription
4. On DNA
• Hormone response element recognized by complex
•
2 must bind (dimerization) for activity
B. Thyroid hormone
•
T3 and T4
•
Based on # of iodines
Fig. 11.5
B. Thyroid hormone
•
•
•
T3 and T4
Based on # of iodines
T4 converted to T3 (active form) in cell
1. Transport
• Most carried on proteins in blood
Fig. 11.3
B. Thyroid hormone
•
•
•
T3 and T4
Based on # of iodines
T4 converted to T3 (active form) in cell
1. Transport
• Most carried on proteins in blood
• Passive diffusion into cell
•
T4 converted to T3 (active form) in cell
1. Transport
• Most carried on proteins in blood
• Passive diffusion into cell
2. Receptor-ligand complex
• Formed in nucleus
• Complex forms
heterodimer
Fig. 11.6
2. Receptor-ligand complex
•
•
•
•
Fig. 11.7
Formed in nucleus
Complex forms heterodimer
Other site bound by receptor-RXR (vit. A)
complex
Transcription produces
specific enzymes
Fig. 11.6
2. Receptor-ligand complex
•
•
•
Formed in nucleus
Complex forms heterodimer
Other site bound by receptor-RXR (vit. A)
complex
•
Transcription produces specific enzymes
C. 2nd messenger – adenylate cyclase
•
Other site bound by receptor-RXR (vit. A) complex
•
Transcription produces specific enzymes
C. 2nd messenger – adenylate cyclase
• Membrane receptor binding
•
Fig. 11.8
Intracellular g-protein  subunit dissociation
C. 2nd messenger – adenylate cyclase
•
•
•
•
Fig. 11.8
Membrane receptor binding
Intracellular g-protein  subunit dissociation
Subunit activates adenylate cyclase
Forms cAMP from ATP
•
Intracellular g-protein  subunit dissociation
•
•
•
Subunit activates adenylate cyclase
Forms cAMP from ATP
cAMP activates protein kinase
Fig. 11.8
•
Subunit activates adenylate cyclase
•
•
•
Forms cAMP from ATP
cAMP activates protein kinase
Protein kinase phosphorylates (adds a phosphate)
specific enzymes
Fig. 11.8
•
Forms cAMP from ATP
•
•
cAMP activates protein kinase
Protein kinase phosphorylates (adds a phosphate)
specific enzymes
•
Enzymes activated or inhibited
Fig. 11.8
•
Forms cAMP from ATP
•
•
cAMP activates protein kinase
Protein kinase phosphorylates (adds a phosphate)
specific enzymes
•
Enzymes activated or inhibited
D. Phospholipase C-Ca++ second messenger
•
•
Membrane receptor binding
G-protein dissociates intracellularly
D. Phospholipase C-Ca++ second messenger
Fig. 11.9
•
•
•
Membrane receptor binding
G-protein dissociates intracellularly
Activates phospholipase C (PLC)
•
•
Releases inositol trisphosphate (IP3) from lipid
IP3 releases Ca++ from endoplasmic reticulum
Fig. 11.9
•
Membrane receptor binding
•
•
•
•
G-protein dissociates intracellularly
Activates phospholipase C (PLC)
Releases inositol trisphosphate (IP3) from lipid
IP3 releases Ca++ from endoplasmic reticulum
•
•
Ca++ activates calmodulin
Calmodulin has a variety of effects