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

Fig. 10.40

• Cones – sense higher level blue, green & red light

3. Receptors

• Rods – sense low levels of light

Fig. 10.36

• Cones – sense higher level blue, green & red light C. Receptor transduction

1. Rhodopsin

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)

Fig. 10.37

2. Light

• Retinene – cis trans configuration

C. Receptor transduction

1. Rhodopsin

• Retinene (photopigment) + opsin (protein)

Fig. 10.37

2. Light

• Retinene – cis trans configuration

C. Receptor transduction

1. Rhodopsin

• Retinene (photopigment) + opsin (protein)

Fig. 10.37

2. Light

• Retinene – cis trans configuration

3. trans Retinene

• Activates g-protein (transducin) cascade

• Closes Na+ channels

• Hyperpolarizes cell

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

• Photoreceptors depolarized and inhibitory

1. Dark

• Inhibit adjacent cells in retina

D. Dark vs. light

• Photoreceptors depolarized and inhibitory

1. Dark

• Inhibit adjacent cells in retina

Fig. 10.39

2. Light

• Photoreceptors inhibitory and depolarized

1. Dark

• Inhibit adjacent cells in retina

2. Light

• Receptors hyperpolarized (inhibited)

Fig. 10.39

• Photoreceptors inhibitory and depolarized

1. Dark

• 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

I. General info.

A. Classifications

Endocrine glands – secrete into blood

Fig. 11.1

Chapter 11 – Endocrine

I. General info.

A. Classifications

Endocrine glands – secrete into blood

1. Amines – derived from single amino acids • Thyroid hormone Fig. 11.3

Fig. 9.9

• Epinephrine

I. General info.

A. Classifications

1. Amines – derived from single amino acids • Thyroid hormone

• Epinephrine

2. Polypeptides – chains of amino acids

• Antidiuretic hormone

disulfide bridges

• Insulin

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

• e.g. – epinephrine & norepi. on heart

2. Permissive

• Additive or complementary

D. Interactions

1. Synergistic

• e.g. – epinephrine & norepi. on heart

2. Permissive

• Additive or complementary

• 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

Fig. 11.5

• 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

Fig. 11.4

• Two complexes bind two receptor half sites on DNA (dimerization)

3. Receptor-ligand complex

• Translocates to nucleus

• Two complexes bind two receptor half sites on DNA (dimerization)

Fig. 11.4

Fig. 11.5

• Form homodimer

• Activate transcription

3. Receptor-ligand complex

• Translocates to nucleus

• Two complexes bind two receptor half sites on DNA (dimerization)

Fig. 11.5

• 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

B. Thyroid hormone

• T3 and T4

• Based on # of iodines

Fig. 11.3

• T4 converted to T3 (active form) in cell

1. Transport

• Most carried on proteins in blood

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 Fig. 11.6

2. Receptor-ligand complex

• Formed in nucleus

• Complex forms heterodimer

Fig. 11.6

2. Receptor-ligand complex

• Formed in nucleus

• Complex forms heterodimer

• Other site bound by receptor-RXR (vit. A) complex

Fig. 11.7

• Transcription produces specific enzymes

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

• Membrane receptor binding

Fig. 11.8

• Intracellular g-protein subunit dissociation

• Subunit activates adenylate cyclase

• Forms cAMP from ATP

Fig. 11.8

• 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

• 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

• Membrane receptor binding

• G-protein dissociates intracellularly

Fig. 11.9

• Activates phospholipase C (PLC)

• Releases inositol trisphosphate (IP3) from lipid

• IP3 releases Ca++ from endoplasmic reticulum

• Membrane receptor binding

• G-protein dissociates intracellularly

Fig. 11.9

• 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