Physiology and Anatomy 1

• Supportive function: stabalise the structure of the neuronal arrangements
• Nutritional function: store energy and provide nutrients to the neurons
• Defense function: Especially microglia cells, they are resident macrophaes in the brain
• Regulate the transmission of electrical excitation in neuronal synapses 

• They form the scaffold of the CNS defining architecture of the brain and spinal cord
• Form glial-vascular barrier: Blood-Brain-Barrier 
• Regulate cerebreal microcirculation
• Regulate extracellular ion concentrations in the brain (K+, H+, glutamate) 
• Provide energy substrates for neurons
• Signaling functions

1. Protecting the brain from foreign substances in the blood that could injure the brain
2. Maintaining a constant environment (homeostasis) for the brain

Potassium outflow during neuronal activity. If [potassium] builds up outside, there will be a problem because neuronal membrane potential depends on low [potassium].

Solution: Astrocytes prevent [potassium] build-up by taking in potassium. This is thought to be due to astrocytic Na⁺/ K⁺ pumo and partly due to K⁺ channels

The neural process that sends the signal or message away from the cell body towards target cells or neurons 

The brain + spinal cord

Nerves beyond the brain and spinal cord

Tree-like extensions of the neural cell body. Recieves chemical neurotransmitter signals or message from other neurons

Nonselective cation channels which allow the flow of K⁺, Na⁺ and Ca²⁺ in response to glutamate binding

Chemical released by nerve terminals at a synapse, that crosses the synapse carrying information from the nerve terminal to the dendrite 

Special molecule on a dendrite that tastes each specific neurotransmitter. Neurotransmitter and receptor must fit together like a lock and key 

Place where one neuron connects to another. It includes the nerve terminal of the first neuron, the place on the second neuron with receptors and the space between them.

The electrical signal in the axon of the first neuron triggers a chemical signal to be releases into the gap that is tasted by receptors in the second neuron

Microglia are the primary immune-competent cells of the central nervous system and have various innate immune functions.

Immune cells cant easily enter the brain because of the blood-brain barrier so the brain has microglia (its own immune cells) 

They engulf and destroy microbes. They can also prune dendrites by pinching off unwanted synapses. 

They provide neurons with myelin sheaths. 

The main function is to electrically insulate the axons by creating the myelin sheath. (same function by schwann cells in the peripheral nervous system) 

• Myelin is an electrically insulating material: essential for proper functioning of neuronal signaling
• Main purpose: increase the speed at which the elect. impulses propagate along the myelinated axon
• Helps prevent the electrical current from leaving the axon 

• Synthesis of neurotransmitters
• Processing of incoming signals 

• Reception of signals from other neurons at the synaptic contants 
• Sensing information from the environment in non synaptic ways

• Conduction of action potentials from the cell body to synapses
• Transport of proteins
• Axonal transport processes 

• Final output station of a neuron: site where electrical impulses are converted into chemical signals
• Form synapses with the dendrites or somata of other neurons 

1. Input area
2. Integratice part
3. Conductile part
4. Output area

Although neurons can differ in shape, location and eventual function, they all have the same principle functional components 

• The neuronal membrane serves as the barrier to enclose the neuronal cytoplasm 
• Principle components: phospholipids and various embedded proteins, especially pores, transporters and receptors 
• The neuronal membrane is essential for neuronal signaling 

• neuronal membrane contains a lot of distict ion channels (passive transport) and transporters (active transport) 
• Ion channels and transporters are membrane-spanning proteins through which selected ion can pass or can activly be transported
• Ion channels and transporters are an essential prerequisite for electrical conduction 

• Sodium-potassium pump is a membrane associated protein that actively transports  Na⁺ and K⁺ against their concentration gradients
• Na⁺ is transported out of the cell ( 3 ions)
• K⁺ is transported into the cell ( only 2 ions)
• This process requires energy (ATP) 
• The sodium potassium pumo is essential for maintaining ion concentration gradients across the neuronal membrane and is critical in establisching the membrane potential of neurons 

1. Intake of food, cutting, grinding
2. Movement of food through GI tract
3. Secretion of digestive juices and digestion
4. Absorption of water, electrolytes, vitamins, digestive products
5. Excretion of unwanted products
6. Control of food intake 

The GI tract has a common structure throughout with local modufication according to specific function. 

Common structure: 

• Muscles
• Nerves
• Epithelium
• Connected glands 

The total fluid volume that passes through the GI tract every day is much larger than the volume that is ingested --> explains why diarrhea can be so dangerous (leads to the loss of much more water than just the ingested fluid. 

H₂O goes in and out of GI tract at various points. If in > out, this can lead to massive dehydration since water that goes in will be excreted. In/ out balance is very important 

• Blood in = superior mesenteric artery
• Blood out = hepatic portal vein

Hepatic portal vein carries everything from GI to liver 

It is all autonomic. 

1. Sensory autonomic
2. Motor autonomic
3. Enteric brain in gut 

Enteric can work independently of CNS.

The enteric nervous system coordinates gut muscle contraction and release of substances from various GI-assiciated glands into GI tract lumen

= crushing / grinding of food

Chewing is very important for increasing surface area for digestion, dissolving food, stimulating taste, releasing saliva. 

Several saliva glands make about 1 L saliva per day. 

Different cells / glands collectibely secrete mucins (lubricant) and amylase. 

Saliva also contributes mucus to stomach which helps various aspects of stomach buffering. 

There are 2 types of secretions: 

1. Serous (all glands):  secretions contain ptyalin
2. Mucous (all exept parotid gland): secretion contains mucins for lubrification and surface protection

Salivary secretion is a 2 stage operation: 

1. involves acini: solution of ions and mucus and amylase
2. involves the salivary ducts 

Why secrete ions? Stuff is carried by water. Ions are an osmotic tool to secrete water 

Taste/Tactile sensory nerves --> brainstem --> parasympathetic motor. 

Salivary glands are controlled by parasympathetic nervous signals from the salivatory nuclei in the brain stem. These nuclei are excited by taste and tactile stimuli from the tongue and other areas of the mouth. 

Salivation can also be stimulated or inhibited by nervous signals arriving in the salivatory nuclei from higher centers of the CNS --> memory-related control from higher brain centers (Pavolov) 

Nerve signals stimulate secretion by causing the contractions of myoepithelial cells that surround the acini of the glands. 

Neural signals cause secretion by both controlling acinar cells (fluid, mucins, enzymes secretion) and duct muscles 

• Lubricates food during chewing
• Has a cleaning, antibacterial and antiviral effect
• Decrease in salivary flow leads to dry mouth feeling --> thirst --> regulation of fluid homeostasis