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Nervous and Chemical Regulation
Nervous System- Chapter 35 Endocrine System- Chapter 39, Sections 1 and 2
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Regulation An organism’s environment is always changing
An organism needs to respond to these changes Responses need to be regulated and coordinated Irritability- the ability to respond to changes in the environment In complex organisms the nervous and endocrine systems control regulation
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Regulation in Protists (Amoeba and Paramecium)
No true nervous system Do move away from strong light and harmful chemicals Move toward food Cilia’s beating is controlled
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Regulation in the Hydra
Has a nervous net which reaches all cells No organized center When 1 area is stimulated, the entire organism responds
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Regulation in the Earthworm
Has a central nervous system Includes “brain” connected to 2 ventral nerve cords which enlarge into ganglia in each segment Ganglia- group of cell bodies and interneurons that relay and coordinate nerve impulses
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Earthworm (continued)
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Regulation in the Grasshopper
Similar to the earthworm Has a “brain”, ganglia, ventral nerve cords Has sense organs which are more developed- eyes, antennae, taste organs, sensitive to sound
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Grasshopper (continued)
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Mechanisms of Nervous Regulation
Nerve cells carry impulses (messages) throughout the organism Receptors (sense organs) perceive changes in the environment Message is sent from the receptor over a pathway of nerve cells to effector (gland or muscle) Effector responds to change
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Mechanisms of Nervous Regulation (continued)
Stimulus is the change in the environment which causes the receptor to send the message Brain- a group of nerve cells which coordinate and control the nervous system (interneurons)
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Structure of Neurons Nerve cell = neuron
Can send electrical and chemical impulses along the cell membrane
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3 Parts of a Neuron 1) Cell Body- contains the nucleus and organelles
2) Dendrite- short, highly branched fibers that receive the impulse 3) Axon- long, thin fiber that extends from the cell body and carries the impulse away from the cell Axon or dendrite is called the nerve fiber The impulse is carried across the synapse (space between them)
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Diagram of Nerve Synapse
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Types of Nerves Nerves are bundles of axons and dendrites bound together (you already know this) Sensory nerves (sensory neuron)- carry impulse from the receptor to the spinal cord and brain Interneuron - transmits impulses between sensory and motor neurons (the brain and spinal cord) Motor nerves (motor neuron)- carry the impulse from the brain and spinal cord to the effector Mixed nerves have both sensory and motor
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Types of Nerves
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Pathway of Nervous System
Stimulus → Receptor → Impulse → (touch hot) (skin) (sensory nerve) Brain → Impulse → Effector (motor nerve) (muscles pull hand away)
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Transmission at Synapses
The impulse must be carried over the gap (synapse) Chemical neurotransmitters (acetylcholine and norepinephrine) are at the end of the axon The neurotransmitters cross the gap and start the impulse in the next nerve cell
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Diagram of Neurotransmitter
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Drugs and the Nervous System
Certain drugs interfere with the nervous system Paralysis can result from neurotransmitters not being able to cross the synapse (can lead to death) Stimulants increase the amount of neurotransmitters Depressants block neurotransmitters LSD interferes with a neurotransmitter
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Human Nervous System- Central Nervous System
Contains the brain and spinal cord Controls most body activities Skull and spinal column protect the brain and spinal cord Meninges- are 3 tough membranes that also protect the brain and spinal cord Cerebrospinal fluid (CSF) fills the space between the membranes and cushions against shock
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Human Nervous System- Central Nervous System
YouTube - The Brain 25 Frontal Lobes and Behavior The Story of Phineas Gage 1
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Brain Is very active, uses a lot of glucose Parts of the Brain
Thalamus- relay center between parts of the brain and spinal cord, receives sensory information Hypothalamus- controls body temperature, blood pressure, sleep, emotions, endocrine system
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Parts of the Brain (continued)
Pons- relay system linking spinal cord and brain Brainstem- consists of: pons, medulla oblongata, and midbrain Cerebrum- largest part highly developed divided into 2 halves called hemispheres different areas are responsible for different functions (hearing, vision, thought, memory)
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Parts of the Brain (continued)
Cerebellum- Below and to the rear of the cerebrum Works with the cerebrum to coordinate muscle movement and balance Medulla Oblongata- Controls many involuntary activities (breathing, heartbeat)
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Spinal Cord Connects the brain and the PNS
Sensory impulses travel up the cord to the brain Motor impulses travel down the cord to effectors Controls certain reflexes Involuntary, automatic responses to certain stimuli Blinking, sneezing, knee-jerk Reflex arc- pathway goes through the spinal cord, NOT the brain
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Sense Receptors Eye- Ear- For hearing and balance
Gives humans most information Light enters the eye and the image forms on the retina Ear- For hearing and balance Vibrations in the air enter inner ear and impulses travel to brain
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Sense Receptors (continued)
Skin- Have specific skin receptors for pain, touch, cold, heat, pressure Are distributed differently in different parts of the body Taste- Taste buds contact neurons Certain taste buds are responsible for certain tastes
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Sense Receptors (continued)
Smell- Have olfactory cells in upper nasal cavity Connected to brain through olfactory nerves
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Disorders Polio Stroke Meningitis Cerebral palsy
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Chemical Regulation- Endocrine System
Releases chemicals into the bloodstream to regulate homeostasis Chemical reaches the proper organ and a response occurs Chemicals produce a slower, longer-lasting response than the nervous system
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Glands Organs which secrete substances
Exocrine- have ducts for secretions Endocrine- are ductless, secretions go directly into the blood (hormones)
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Hormones Are chemical messengers Target 1 specific area of the body
There are 2 types- Protein type- too big to pass through cell membrane (insulin) Steroid type- can pass through cell membrane (estrogen)
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Hormones (continued) Prostaglandins- hormones that do not enter the bloodstream Work on blood pressure, heart rate and other areas
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Hormone Regulation- Positive Feedback
One change causes a second change, which reinforces the first change ↑in chemical A ⇨ an ↑in chemical B which ⇨ a further ↑in chemical A
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Negative Feedback One change causes a second change which opposes the first change ↑in chemical A ⇨ ↑in chemical B which ⇨ ↓in chemical A An example of negative feedback is the thermostat in your house In organisms, this helps to maintain homeostasis
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Mechanisms of Hormone Action
One Messenger Model Steroid hormone enters a target cell (only the target cell will allow the hormone in) The hormone will bind with a receptor protein in the cell The hormone receptor complex will then bring about the change in the cell
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Diagrams of Mechanisms of Hormone Action
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Mechanisms of Hormone Action (continued)
Two Messenger Model Protein (non-steroidal) hormone binds with a receptor on the cell membrane This type of hormone can not enter the cell Enzymes inside the cell are activated and the effect is produced
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Human Endocrine System
May have hypersecretion (too much) of a hormone secreted May have hyposecretion (too little) of a hormone secreted Either one leads to disorders
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Pituitary and Hypothalamus
Are in the brain Hypothalamus links nervous and endocrine systems Pituitary- Controls other glands Secretes many hormones Growth hormone- controls growth Hormones controlling development and release of eggs, milk production, reabsorption of water in the kidneys
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Thyroid In the neck Secretes thyroxine which regulates metabolism
The release of thyroxine is controlled by a negative feedback mechanism
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Parathyroid In the thyroid There are 4 parathyroid glands
Secrete parathyroid hormone which regulates calcium and phosphate levels in the blood
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Goiter A deficiency of iodine in the diet causes a malfunction in the thyroid
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Adrenal On top of the kidneys Hormones help body deal with stress
Epinephrine- secreted in response to sudden stress Breathing, heart rate, sweating, blood pressure all increase
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Adrenal (continued) Corticosteroids-
Cortisol- important in regulating the glucose level in the blood Cortisone- decreases swelling Aldosterone- maintains mineral balance in blood
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Pancreas (Islets of Langerhans)
Both exocrine (digestive enzymes) and endocrine (insulin and glucagon) Insulin- Affects glucose metabolism ↑ movement of glucose into body cells ↑change of glucose to glycogen
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Pancreas (continued) Glucagon-
↑ change of glycogen to glucose ↑ blood glucose levels Diabetes- disease where the pancreas does not produce enough insulin and blood glucose levels are not controlled
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