Chapter 23

Nervous System – rapid response to environmental changes Via electrical signals Endocrine System – chemical signals via blood Hormones Response is slower, but changes can be more long term

Nerve cell = Neuron Cells of all types are irritable and can spread an electrical signal Neurons are specialized for role

When a neuron is not firing = resting potential -70mV (inside relative to outside) Ion concentrations across membrane create it K + move freely down concentration gradient Na + are blocked Active transport – uses energy Na + K + pump

Once charge difference is great enough, the + charge outside the axon stops the movement of K + out and maintains the charge difference at the balance point of -70mV

a) Concentration gradient of Na + and the attractive negative charge inside the axon membrane b) Concentration of K + and the number of proteins inside the axon membrane c) Concentration gradient of Na + and the attractive negative charge outside the axon membrane d) Concentration of K + and the sodium pump

Myelin sheath speeds up conduction of electrical signal in mammals Depolarization actually jumps from node to node between the Schwann cells Saltatory transmission is 2-20X faster

All or none response Variation in intensity of signal is then reflected in the number of action potential spikes/ sec Time

a) Neurotransmitter receptors are in dendrite membrane only. b) Neurotransmitter receptors are in axon membrane only. c) Neurotransmitter is released from the cell body of only one neuron. d) Matching neurotransmitters are released by the synaptic terminal of one neuron and dendrites of a second neuron.

Sensory Neuron – picks up info from a sensory receptor Interneuron – in CNS Integrates info Can be excitatory or inhibitory Motor Neuron – carries response to muscle or gland (effector)

a) Motor neuron, sensory neuron, interneuron b) Interneuron, motor neuron, sensory neuron c) Sensory neuron, interneuron, motor neuron d) Sensory neuron, motor neuron, interneuron

1. Presence of nerves – absent in sponges 2. One-way synapse – 2 way in Cnidarian nerve nets 3. Centralization – concentration of nerves along the midline and the development of a major region of integration, the brain 4. Sheathing – insulation + speed

Central Nervous System Brain Spinal cord Peripheral Nervous System Cranial nerves Ganglia outside CNS Spinal nerves

Hindbrain – Medulla & Pons Passes info between brain + nerve cord Vital centers for heart, blood pressure, respiration Cerebellum Coordinates equilibrium and movement Midbrain – Sends sensory data to higher brain centers

Forebrain – Cerebrum Sensory + motor association Intelligence + memory Written and spoken language Thalamus – sensory integration Hypothalamus – Emotional states Temperature regulation CNS link to endocrine system Pituitary Gland – Master Gland Controlled by Hypothalamus

a) Synaptic terminals, dendrite, myelin sheathing b) Neuron cell body, dendrite, synaptic sheathing c) Dendrites, axon, myelin sheathing d) Axons, dendrite, cell body A B C

All neurons that pass in and out of the CNS Includes: Sensory neurons Voluntary motor neurons Autonomic nervous system (involuntary motor ns) Parasympathetic system Sympathetic system Enteric division

a) The neuron’s action potential b) +40 mV c) The neuron’s resting potential d) The movement of sodium ions into the neuron.

Sensory receptors are our window on the world. Depending on the species, this window can be very different Heat sensors linked to visual pathways in snakes Chemical landscape of army ants Transduction Sensory receptors register an external phenomenon such as light, heat, movement, chemicals in water or air and translate it into an electrical signal in the nervous system.

Detect chemicals in air or dissolved in liquid May be hair or pit with pores for letting chemicals in air or liquid into a sensory receptor cell or directly to the dendrite of a sensory neuron Sensory receptor cell/sensory neuron have specific receptors for specific chemicals When chemical binds to the receptor, sodium channels get leaky = receptor potential Strong enough signal causes an action potential in the sensory neuron – communicating with CNS

Wavelengths – visual spectrum, ultraviolet, infrared, electrical fields Photoreceptors – eyes Take light and convert to an electrical signal

We’ll cover these and other sensory systems in lab Many animals have a totally different perspective of the world because they have different sensory receptors

More about the Skeletal System will be covered in lab.

Endocrine glands Ductless Secrete hormone Hormone signal travels via the circulatory system Target cells/organs have receptors specific for hormone Produces a response – longer term change than NS Negative Feedback Loop

Nerve cell – capable of receiving and sending an electrical signal down its axon Also makes + secretes hormone that then travels in the blood Located in hypothalamus of brain

Can be exciters or inhibitors of a change Some regulate the internal environment Water balance or metabolic rates Some regulate changes in the body Sexual maturity and pregnancy Some regulate responses to gradual environmental changes Migratory behavior, hibernation, rhythmic behavior such as feeding, sleeping, etc.

Hypothalamus – Region of brain Neurosecretory cells Nerve cells go to posterior pituitary Hormone connection to anterior pituitary Pituitary = Master Gland of Endocrine System

Posterior PituitaryAnterior Pituitary

TRH – TSH releasing hormone Thyroxine secreted by Thyroid Increases metabolic rate of cells Production of thyroxine and its activity inhibit production of TRH +TSH Thyroxine secretion slows

Parathyroid – embedded in back of thyroid Parathyroid hormone (PTH) stimulates release of Ca ++ ions from bone

Adrenal cortex –(outer layer) – hormone action: Carbohydrate, protein and lipid metabolism Salt and water balance Adrenal medulla –(inner core) – hormone action: Regulates blood sugar, dilates blood vessels, heart rate Pancreas – insulin and glucagon – hormone action: Lowers blood sugar, stimulates glycogen storage Stimulates the breakdown of glycogen and increase of blood sugar Gonads – testes and ovaries – hormone action: Sexual characteristics, pregnancy, egg + sperm development Pineal Gland- melatonin – regulates circadian rhythms