Week 26 - Nervous system II

• All cells in the body maintain a potential (voltage) difference across the cell membrane, which is the cell’s membrane potential.
• Neurons and muscles (excitable cells) can alter their membrane potential in response to stimulation.
• The membrane potential at rest (cells not actively signalling) is the resting membrane potential.
• The plasma membrane is the membrane that surrounds the cell.
• Gated Channels Control Ion Permeability of Neuronal Membrane.
• Channels may be gated (opened or closed) by various factors including voltage, neurotransmitters (Chemically gated), mechanical means (Mechanically gated) such as stretch, vibration.
• Voltage-gated channels control ion movements during action potentials: they open and close in response to membrane potential changes and are selective for particular ions.
• Changes in membrane potential give rise to action potentials, which are nerve impulses.
• In a typical neuron, action potentials are generated at the axon hillock and are conducted down the axon to the presynaptic terminal.
• When an action potential reaches the axon terminal, the electrical signal is passed to the associated neuron or muscle cell at the synapse, a process known as synaptic transmission.
• Electrical signalling depends on changes in membrane potential due to changes in membrane ion permeability and ion distribution.
• A significant change in membrane potential occurs with the movement of a small number of ions.
• Urinary retention occurs during sympathetic function.
• Relative Na+ and K+ concentrations inside & outside the cell remain unchanged.
• Sympathetic function is part of the autonomic nervous system (ANS) and is associated with the "fight or flight" response.
• The release of urine occurs during parasympathetic function.
• Digestive tract motility and secretion decrease during sympathetic function.
• The pancreas secretes decreased enzymes during sympathetic function.
• Parasympathetic function is also part of the autonomic nervous system (ANS) and is associated with the "rest and digest" response.
• Enzyme secretion increases during sympathetic function.
• The autonomic nervous system (ANS) works closely with the endocrine system and behavioral state system to maintain homeostasis in the body.
• Bronchiolar constriction and dilation are associated with sympathetic function.
• Bladder function changes during sympathetic function.
• During parasympathetic function, the heart rate slows down.
• The kidney increases renin secretion during sympathetic function.
• Insulin secretion is inhibited during sympathetic function.
• Homeostasis involves the dynamic balance between the sympathetic and parasympathetic divisions (branches) of the ANS.
• The heart rate increases and the force of contraction increases during sympathetic function.
• Sympathetic and parasympathetic neurons tend to have opposing effects and are therefore often active in different situations.
• Two sources of resistance to current flow are the cell membrane and the internal resistance of cytoplasm.
• The phospholipid bilayer is an insulator of the cell membrane and no open ion channels are resistance.
• Opening of ion channels is equivalent to membrane resistance.
• The internal resistance of most neurons is determined by the composition of cytoplasm and the diameter of the cell.
• Graded Potentials are variable strength signals that travel over short distances (local current flow).
• A competing ligand can be either an Agonist which binds to and activates the receptor or an Antagonist which binds to and blocks receptor activity.
• Receptors for Norepinephrine (Adrenergic Receptors) are located in smooth muscle cells of blood vessels and heart muscle.
• Norepinephrine (NE) is also known as noradrenaline (NA).
• Receptors for acetylcholine (ACH)/Cholinergic Receptors include the Nicotinic ACH receptor (nACHR) which is activated by nicotine and the Muscarinic ACH receptor (mACHR) which is activated by muscarine (fungi).
• Nervous systems can have synaptic plasticity that is long, short, and both long and short term, meaning changes occur after several hours, several minutes, and both several hours and several minutes.
• Nervous systems can change activity at synapses, a process known as synaptic plasticity, which can be short or long term.