Chapter 2- Brain cells and nervous system organization Flashcards
(112 cards)
Are reactions to the environment always planned?
Sometimes reactions to the environment are planned, some aren’t. Actions like squinting in bright light is unplanned, while drinking water is planned
2 general cell types of the nervous system
- Neurons- transmit information
2. Glia- act as supporting cells
Circuit
Neurons are organized in a precise order to form a circuit. A circuit is how information flows from one place to another. The two neurons could be close together or far apart (like with spinal reflexes).
Synapse
The synapse is the physical connection between 2 neurons where information crosses. This is how neurons communicate, and a single neuron could synapse with many other neurons at once.
All behavior arises from
Neurons- even if they’re few in number
Sensory neurons
Receive input
Motor neurons
Let the body move in a coordinated manner
Interneurons
Neurons that process information between sensory and motor neurons
Roundworm nervous system
302 neurons total, and they have a ganglion rather than a brain. Have very simple behaviors- move toward “good” things and away from bad things- based on light, pressure, moisture, etc.. Their sensory neurons detect light, smell, the presence of water, pressure. Because they have so few neurons, all of their neurons have been mapped. They are arranged in simple circuits that can produce simple behavior
Gill withdrawal reflex in sea slugs
A sea slug’s gill is retracted if you poke it- this is a protective reflex. However, if the tail is poked for a specific amount of times, it will stop retracting. The animals learned this after about 5 pokes,
For all mammals, the nervous system is divided into
The central nervous system (brain and spinal cord) and peripheral nervous system
Divisions of the peripheral nervous system (3)
- Sympathetic nervous system- fight or flight
- Parasympathetic nervous system- rest and digest, normal breathing and blood pressure
- Enteric nervous system- controls the gastrointestinal tract
How does having more neurons affect circuits?
More neurons- more complex circuits- more complex functions
The human nervous system
Has about 80 billion neurons, but also makes connections with hundreds of thousands of other neurons. Still uses sensory neurons to send info to the brain, interneurons process and make decisions, then send information to motor neurons. Humans have more neurons, more discrete brain regions, more complex circuits- capable of abilities that no other species on earth has.
Neurons
Neurons are the building blocks of the nervous system and the element of processing information. They are connected to each other via synapses to form circuits in all species
What aspects of the nervous system are shared between species?
Certain aspects of the nervous system are shared across all species (sensory neurons) and especially closely related species (brain and spinal cord in mammals).
Do circuits formed by neurons drive behavior in all animal species?
Yes, true for all animals
Camillo Golgi
Came up with staining technique to visualize the entire neuron. Thought neurons were continuous like tubing (not true)- he noticed that the processes of one neuron were very close to the other, and they looked like they touch under a microscope
Santiago Ramon y Cajal
Used Golgi’s method. Thought that neurons came close to each other, but did not touch (true)- there’s a small gap in between processes (this is the synapse). Also came up with the neuron doctrine
Neuron doctrine (2)
States that each neuron is an independent unit (a single processing unit) and information must be transmitted across gaps between neurons (synapses).
Neurons are polarized- what does this mean?
Polarized means that there is a direction to neurons- they aren’t symmetrical. There’s an input zone, then integration zone, conduction zone, and output zone.
Dendrites and spines
Dendrites look like branches, while spines look like mushroom shaped protrusions from the dendrites. These structures are the input zone- where information/chemical signals are received from other neurons
Soma
The cell body- this is the integration zone. The soma processes the electric information and decides what its response will be (or if it will even respond). Also contains organelles like the mitochondria, cell nucleus, and ribosomes.
Mitochondria function
Produce energy