Animal Physiology Nervous System Organization

What is evolutionarily true of neurotransmitters?

they are evolutionarily ancient and are essentially the same regardless of what kind of animal you are looking at

• differences stem from the organizations of nervous systems that gives varying levels of complexity

What animal doesn’t have a nervous system?

Sponge; although they do have the components of a nervous system

Ganglia in vertebrates

collection of cells apart from the brain where local integration happens (interneurons)

All vertebrates…

must do basic homeostasis so you will find the same kinds of homeostatic control systems and deep brain structures responsible for them (i.e. brainstem, hypothalamus, cortex, etc.)

• thin cortex=less complex; thick cortex=more complex

Advantages and disadvantages of sensory straight to motor pathway with only one interneuron (monosynaptic)

advantage: super fast and are often involved in reflexes (protective mechanisms)

disadvantage: output is always going to be the same because there is no room for modulation

Vertebrate nervous system

CNS consists of brain and spinal cord

• brain stem is for basic survival stuff and then cortex builds on top of this for complexity

spinal cord cross section:

• sensory info coming from periphery goes into spinal cord via dorsal root

• interneurons solely in CNS

• motor info comes out after interneurons and travels out of spinal cord via ventral root

Divisions of the nervous system are…

anatomical not functional

• somatic sensory: special senses, touch, etc

• autonomic: involuntary, visceral study

• somatic motor: voluntary motor

• autonomic motor input: involuntary things to keep you alive

  • sympathetic: flight/fight

  • parasympathetic: rest/digest

Enteric nervous system

in the gut

looks more so like that of a jellyfish → decentralized nerve net

Peripheral ganglia

places where you have synapses happening out in the periphery

• specific to autonomic nervous system

Two flavors of motor

somatic: voluntary skeletal muscles

• acetylcholine neurotransmitter

• cell body lives in CNS

• monosynaptic so no modulation

autonomic: involuntary

• cell body in CNS that sends axon out to but there is another synapse in periphery (ganglion)

• all preganglionic release acetylcholine neurotransmitter

  • sympathetic postganglionic: epinephrine/norepinephrine

  • parasympathetic postganglionic: acetylcholine

Sympathetic vs parasympathetic

Sympathetic: thoracolumbar

• preganglionic: acetylcholine; postganglionic: norepinephrine/epinephrine

  • cholinergic and adrenergic

• short preganglionic and long postganglionic

• has endocrine component to use blood to get message out quickly (adrenal gland dumps epinephrine into blood so anyone with a receptor responds)

Parasympathetic: craniosacral

• acetylcholine is neurotransmitter for pre and postganglionic

  • cholinergic

• long preganglionic and short postganglionic

Circadian Rhythm

endogenous (inside of you and don’t need outside input)

does involve environmental cues though (entrainment)

• zeitgeber (time giver): light for us; ocean tides for other animals

Suprachiasmatic nucleus (SCN)

-drives the pineal gland which releases melatonin (hormone so travels everywhere) and every single cell in your body knows what time it is and what it should be doing at that time

-sits right above visual input (above optic chiasm)

Biological clocks are under what kind of control?

feed-forward control

-self-inhibiting cycle of clock genes as they dimerize and inhibit their own transcription

• PER/CRY (transcription factors that turn things on and off to inhibit themselves)

• CLOCK/BMAL